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rfc:rfc3780

Network Working Group F. Strauss Request for Comments: 3780 TU Braunschweig Category: Experimental J. Schoenwaelder

                                       International University Bremen
                                                              May 2004
    SMIng - Next Generation Structure of Management Information

Status of this Memo

 This memo defines an Experimental Protocol for the Internet
 community.  It does not specify an Internet standard of any kind.
 Discussion and suggestions for improvement are requested.
 Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

 This memo defines the base SMIng (Structure of Management
 Information, Next Generation) language.  SMIng is a data definition
 language that provides a protocol-independent representation for
 management information.  Separate RFCs define mappings of SMIng to
 specific management protocols, including SNMP.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  The History of SMIng . . . . . . . . . . . . . . . . . .  4
     1.2.  Terms of Requirement Levels. . . . . . . . . . . . . . .  5
 2.  SMIng Data Modeling. . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Identifiers. . . . . . . . . . . . . . . . . . . . . . .  6
 3.  Base Types and Derived Types . . . . . . . . . . . . . . . . .  7
     3.1.  OctetString. . . . . . . . . . . . . . . . . . . . . . .  8
     3.2.  Pointer. . . . . . . . . . . . . . . . . . . . . . . . .  9
     3.3.  ObjectIdentifier . . . . . . . . . . . . . . . . . . . .  9
     3.4.  Integer32. . . . . . . . . . . . . . . . . . . . . . . . 10
     3.5.  Integer64. . . . . . . . . . . . . . . . . . . . . . . . 11
     3.6.  Unsigned32 . . . . . . . . . . . . . . . . . . . . . . . 12
     3.7.  Unsigned64 . . . . . . . . . . . . . . . . . . . . . . . 13
     3.8.  Float32. . . . . . . . . . . . . . . . . . . . . . . . . 13
     3.9.  Float64. . . . . . . . . . . . . . . . . . . . . . . . . 14
     3.10. Float128 . . . . . . . . . . . . . . . . . . . . . . . . 15
     3.11. Enumeration. . . . . . . . . . . . . . . . . . . . . . . 17
     3.12. Bits . . . . . . . . . . . . . . . . . . . . . . . . . . 17

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     3.13. Display Formats. . . . . . . . . . . . . . . . . . . . . 18
 4.  The SMIng File Structure . . . . . . . . . . . . . . . . . . . 20
     4.1.  Comments . . . . . . . . . . . . . . . . . . . . . . . . 20
     4.2.  Textual Data . . . . . . . . . . . . . . . . . . . . . . 21
     4.3.  Statements and Arguments . . . . . . . . . . . . . . . . 21
 5.  The module Statement . . . . . . . . . . . . . . . . . . . . . 21
     5.1.  The module's import Statement. . . . . . . . . . . . . . 22
     5.2.  The module's organization Statement. . . . . . . . . . . 23
     5.3.  The module's contact Statement . . . . . . . . . . . . . 23
     5.4.  The module's description Statement . . . . . . . . . . . 23
     5.5.  The module's reference Statement . . . . . . . . . . . . 23
     5.6.  The module's revision Statement. . . . . . . . . . . . . 23
           5.6.1. The revision's date Statement . . . . . . . . . . 24
           5.6.2. The revision's description Statement. . . . . . . 24
     5.7.  Usage Example. . . . . . . . . . . . . . . . . . . . . . 24
 6.  The extension Statement. . . . . . . . . . . . . . . . . . . . 25
     6.1.  The extension's status Statement . . . . . . . . . . . . 25
     6.2.  The extension's description Statement. . . . . . . . . . 26
     6.3.  The extension's reference Statement. . . . . . . . . . . 26
     6.4.  The extension's abnf Statement . . . . . . . . . . . . . 26
     6.5.  Usage Example. . . . . . . . . . . . . . . . . . . . . . 26
 7.  The typedef Statement. . . . . . . . . . . . . . . . . . . . . 27
     7.1.  The typedef's type Statement . . . . . . . . . . . . . . 27
     7.2.  The typedef's default Statement. . . . . . . . . . . . . 27
     7.3.  The typedef's format Statement . . . . . . . . . . . . . 27
     7.4.  The typedef's units Statement. . . . . . . . . . . . . . 28
     7.5.  The typedef's status Statement . . . . . . . . . . . . . 28
     7.6.  The typedef's description Statement. . . . . . . . . . . 29
     7.7.  The typedef's reference Statement. . . . . . . . . . . . 29
     7.8.  Usage Examples . . . . . . . . . . . . . . . . . . . . . 29
 8.  The identity Statement . . . . . . . . . . . . . . . . . . . . 30
     8.1.  The identity's parent Statement. . . . . . . . . . . . . 30
     8.2.  The identity's status Statement. . . . . . . . . . . . . 30
     8.3.  The identity' description Statement. . . . . . . . . . . 31
     8.4.  The identity's reference Statement . . . . . . . . . . . 31
     8.5.  Usage Examples . . . . . . . . . . . . . . . . . . . . . 31
 9.  The class Statement. . . . . . . . . . . . . . . . . . . . . . 32
     9.1.  The class' extends Statement . . . . . . . . . . . . . . 32
     9.2.  The class' attribute Statement . . . . . . . . . . . . . 32
           9.2.1. The attribute's type Statement. . . . . . . . . . 32
           9.2.2. The attribute's access Statement. . . . . . . . . 32
           9.2.3. The attribute's default Statement . . . . . . . . 33
           9.2.4. The attribute's format Statement. . . . . . . . . 33
           9.2.5. The attribute's units Statement . . . . . . . . . 33
           9.2.6. The attribute's status Statement. . . . . . . . . 34
           9.2.7. The attribute's description Statement . . . . . . 34
           9.2.8. The attribute's reference Statement . . . . . . . 34
     9.3.  The class' unique Statement. . . . . . . . . . . . . . . 35

Strauss & Schoenwaelder Experimental [Page 2] RFC 3780 SMIng May 2004

     9.4.  The class' event Statement . . . . . . . . . . . . . . . 35
           9.4.1. The event's status Statement. . . . . . . . . . . 35
           9.4.2. The event's description Statement . . . . . . . . 35
           9.4.3. The event's reference Statement . . . . . . . . . 36
     9.5.  The class' status Statement. . . . . . . . . . . . . . . 36
     9.6.  The class' description Statement . . . . . . . . . . . . 36
     9.7.  The class' reference Statement . . . . . . . . . . . . . 37
     9.8.  Usage Example. . . . . . . . . . . . . . . . . . . . . . 37
 10. Extending a Module . . . . . . . . . . . . . . . . . . . . . . 38
 11. SMIng Language Extensibility . . . . . . . . . . . . . . . . . 39
 12. Security Considerations. . . . . . . . . . . . . . . . . . . . 41
 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 41
 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42
     14.1. Normative References . . . . . . . . . . . . . . . . . . 42
     14.2. Informative References . . . . . . . . . . . . . . . . . 42
 Appendix A.  NMRG-SMING Module . . . . . . . . . . . . . . . . . . 44
 Appendix B.  SMIng ABNF Grammar. . . . . . . . . . . . . . . . . . 53
 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 63
 Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 64

1. Introduction

 In traditional management systems, management information is viewed
 as a collection of managed objects, residing in a virtual information
 store, termed the Management Information Base (MIB).  Collections of
 related objects are defined in MIB modules.  These modules are
 written in conformance with a specification language, the Structure
 of Management Information (SMI).  There are different versions of the
 SMI.  The SMI version 1 (SMIv1) is defined in [RFC1155], [RFC1212],
 [RFC1215], and the SMI version 2 (SMIv2) in [RFC2578], [RFC2579], and
 [RFC2580].  Both are based on adapted subsets of OSI's Abstract
 Syntax Notation One, ASN.1 [ASN1].
 In a similar fashion, policy provisioning information is viewed as a
 collection of Provisioning Classes (PRCs) and Provisioning Instances
 (PRIs) residing in a virtual information store, termed the Policy
 Information Base (PIB).  Collections of related Provisioning Classes
 are defined in PIB modules.  PIB modules are written using the
 Structure of Policy Provisioning Information (SPPI) [RFC3159] which
 is an adapted subset of SMIv2.
 The SMIv1 and the SMIv2 are bound to the Simple Network Management
 Protocol (SNMP) [RFC3411], while the SPPI is bound to the Common Open
 Policy Service Provisioning (COPS-PR) Protocol [RFC3084].  Even
 though the languages have common rules, it is hard to use common data
 definitions with both protocols.  It is the purpose of this document
 to define a common data definition language, named SMIng, that can

Strauss & Schoenwaelder Experimental [Page 3] RFC 3780 SMIng May 2004

 formally specify data models independent of specific protocols and
 applications.  The appendix of this document defines a core module
 that supplies common SMIng definitions.
 A companion document contains an SMIng language extension to define
 SNMP specific mappings of SMIng definitions in compatibility with
 SMIv2 MIB modules [RFC3781].  Additional language extensions may be
 added in the future, e.g., to define COPS-PR specific mappings of
 SMIng definitions in a way that is compatible with SPPI PIBs.
 Section 2 gives an overview of the basic concepts of data modeling
 using SMIng, while the subsequent sections present the concepts of
 the SMIng language in detail: the base types, the SMIng file
 structure, and all SMIng core statements.
 The remainder of the document describes extensibility features of the
 language and rules to follow when changes are applied to a module.
 Appendix B contains the grammar of SMIng in ABNF [RFC2234] notation.

1.1. The History of SMIng

 SMIng started in 1999 as a research project to address some drawbacks
 of SMIv2, the current data modeling language for management
 information bases.  Primarily, its partial dependence on ASN.1 and a
 number of exception rules turned out to be problematic.  In 2000, the
 work was handed over to the IRTF Network Management Research Group
 where it was significantly detailed.  Since the work of the RAP
 Working Group on COPS-PR and SPPI emerged in 1999/2000, SMIng was
 split into two parts: a core data definition language (defined in
 this document) and protocol mappings to allow the application of core
 definitions through (potentially) multiple management protocols.  The
 replacement of SMIv2 and SPPI by a single merged data definition
 language was also a primary goal of the IETF SMING Working Group that
 was chartered at the end of 2000.
 The requirements for a new data definition language were discussed
 several times within the IETF SMING Working Group and changed
 significantly over time [RFC3216], so that another proposal (in
 addition to SMIng), named SMI Data Structures (SMI-DS), was presented
 to the Working Group.  In the end, neither of the two proposals found
 enough consensus and support, and the attempt to merge the existing
 concepts did not succeed, resulting in the Working Group being closed
 down in April 2003.
 In order to record the work of the NMRG (Network Management Research
 Group) on SMIng, this memo and the accompanying memo on the SNMP
 protocol mapping [RFC3781] have been published for informational
 purposes.

Strauss & Schoenwaelder Experimental [Page 4] RFC 3780 SMIng May 2004

 Note that throughout these documents, the term "SMIng" refers to the
 specific data modeling language that is specified in this document,
 whereas the term "SMING" refers to the general effort within the IETF
 Working Group to define a new management data definition language as
 an SMIv2 successor and probably an SPPI merger, for which "SMIng" and
 "SMI-DS" were two specific proposals.

1.2. Terms of Requirement Levels

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in [RFC2119].

2. SMIng Data Modeling

 SMIng is a language designed to specify management information in a
 structured way readable to computer programs, e.g., MIB compilers, as
 well as to human readers.
 Management information is modeled in classes.  Classes can be defined
 from scratch or by derivation from a parent class.  Derivation from
 multiple parent classes is not possible.  The concept of classes is
 described in Section 9.
 Each class has a number of attributes.  Each attribute represents an
 atomic piece of information of a base type, a sub-type of a base
 type, or another class.  The concept of attributes is described in
 Section 9.2.
 The base types of SMIng include signed and unsigned integers, octet
 strings, enumeration types, bitset types, and pointers.  Pointers are
 references to class instances, attributes of class instances, or
 arbitrary identities.  The SMIng type system is described in Section
 3.
 Related class and type definitions are defined in modules.  A module
 may refer to definitions from other modules by importing identifiers
 from those modules.  Each module may serve one or multiple purposes:
 o  the definition of management classes,
 o  the definition of events,
 o  the definition of derived types,
 o  the definition of arbitrary untyped identities serving as values
    of pointers,

Strauss & Schoenwaelder Experimental [Page 5] RFC 3780 SMIng May 2004

 o  the definition of SMIng extensions allowing the local module or
    other modules to specify information beyond the scope of the base
    SMIng in a machine readable notation.  Some extensions for the
    application of SMIng in the SNMP framework are defined in
    [RFC3781],
 o  the definition of information beyond the scope of the base SMIng
    statements, based on locally defined or imported SMIng extensions.
 Each module is identified by an upper-case identifier.  The names of
 all standard modules must be unique (but different versions of the
 same module should have the same name).  Developers of enterprise
 modules are encouraged to choose names for their modules that will
 have a low probability of colliding with standard or other enterprise
 modules, e.g., by using the enterprise or organization name as a
 prefix.

2.1. Identifiers

 Identifiers are used to identify different kinds of SMIng items by
 name.  Each identifier is valid in a namespace which depends on the
 type of the SMIng item being defined:
 o  The global namespace contains all module identifiers.
 o  Each module defines a new namespace.  A module's namespace may
    contain definitions of extension identifiers, derived type
    identifiers, identity identifiers, and class identifiers.
    Furthermore, a module may import identifiers of these kinds from
    other modules.  All these identifiers are also visible within all
    inner namespaces of the module.
 o  Each class within a module defines a new namespace.  A class'
    namespace may contain definitions of attribute identifiers and
    event identifiers.
 o  Each enumeration type and bitset type defines a new namespace of
    its named numbers.  These named numbers are visible in each
    expression of a corresponding value, e.g., default values and
    sub-typing restrictions.
 o  Extensions may define additional namespaces and have additional
    rules of other namespaces' visibility.
 Within every namespace each identifier MUST be unique.

Strauss & Schoenwaelder Experimental [Page 6] RFC 3780 SMIng May 2004

 Each identifier starts with an upper-case or lower-case character,
 dependent on the kind of SMIng item, followed by zero or more
 letters, digits, and hyphens.
 All identifiers defined in a namespace MUST be unique and SHOULD NOT
 only differ in case.  Identifiers MUST NOT exceed 64 characters in
 length.  Furthermore, the set of all identifiers defined in all
 modules of a single standardization body or organization SHOULD be
 unique and mnemonic.  This promotes a common language for humans to
 use when discussing a module.
 To reference an item that is defined in the local module, its
 definition MUST sequentially precede the reference.  Thus, there MUST
 NOT be any forward references.
 To reference an item that is defined in an external module it MUST be
 imported (Section 5.1).  Identifiers that are neither defined nor
 imported MUST NOT be visible in the local module.
 When identifiers from external modules are referenced, there is the
 possibility of name collisions.  As such, if different items with the
 same identifier are imported or if imported identifiers collide with
 identifiers of locally defined items, then this ambiguity is resolved
 by prefixing those identifiers with the names of their modules and
 the namespace operator `::', i.e., `Module::item'.  Of course, this
 notation can be used to refer to identifiers even when there is no
 name collision.
 Note that SMIng core language keywords MUST NOT be imported.  See the
 `...Keyword' rules of the SMIng ABNF grammar in Appendix B for a list
 of those keywords.

3. Base Types and Derived Types

 SMIng has a set of base types, similar to those of many programming
 languages, but with some differences due to special requirements from
 the management information model.
 Additional types may be defined, derived from those base types or
 from other derived types.  Derived types may use subtyping to
 formally restrict the set of possible values.  An initial set of
 commonly used derived types is defined in the SMIng standard module
 NMRG-SMING [RFC3781].
 The different base types and their derived types allow different
 kinds of subtyping, namely size restrictions of octet strings
 (Section 3.1), range restrictions of numeric types (Section 3.4

Strauss & Schoenwaelder Experimental [Page 7] RFC 3780 SMIng May 2004

 through Section 3.10), restricted pointer types (Section 3.2), and
 restrictions on the sets of named numbers for enumeration types
 (Section 3.11) and bit sets (Section 3.12).

3.1. OctetString

 The OctetString base type represents arbitrary binary or textual
 data.  Although SMIng has a theoretical size limitation of 2^16-1
 (65535) octets for this base type, module designers should realize
 that there may be implementation and interoperability limitations for
 sizes in excess of 255 octets.
 Values of octet strings may be denoted as textual data enclosed in
 double quotes or as arbitrary binary data denoted as a `0x'-prefixed
 hexadecimal value of an even number of at least two hexadecimal
 digits, where each pair of hexadecimal digits represents a single
 octet.  Letters in hexadecimal values MAY be upper-case, but lower-
 case characters are RECOMMENDED.  Textual data may contain any number
 (possibly zero) of any 7-bit displayable ASCII characters, including
 tab characters, spaces, and line terminator characters (nl or cr &
 nl).  Some characters require a special encoding (see Section 4.2).
 Textual data may span multiple lines, where each subsequent line
 prefix containing only white space up to the column where the first
 line's data starts SHOULD be skipped by parsers for a better text
 formatting.
 When defining a type derived (directly or indirectly) from the
 OctetString base type, the size in octets may be restricted by
 appending a list of size ranges or explicit size values, separated by
 pipe `|' characters, with the whole list enclosed in parenthesis.  A
 size range consists of a lower bound, two consecutive dots `..', and
 an upper bound.  Each value can be given in decimal or `0x'-prefixed
 hexadecimal notation.  Hexadecimal numbers must have an even number
 of at least two digits.  Size restricting values MUST NOT be
 negative.  If multiple values or ranges are given, they all MUST be
 disjoint and MUST be in ascending order.  If a size restriction is
 applied to an already size restricted octet string, the new
 restriction MUST be equal or more limiting, that is, raising the
 lower bounds, reducing the upper bounds, removing explicit size
 values or ranges, or splitting ranges into multiple ranges with
 intermediate gaps.

Strauss & Schoenwaelder Experimental [Page 8] RFC 3780 SMIng May 2004

 Value Examples:
    "This is a multiline
     textual data example."         // legal
    "This is "illegally" quoted."   // illegal quotes
    "This is \"legally\" quoted."   // legally encoded quotes
    "But this is 'ok', as well."    // legal apostrophe quoting
    ""                              // legal zero length
    0x123                           // illegal odd hex length
    0x534d496e670a                  // legal octet string
 Restriction Examples:
    OctetString (0 | 4..255)        // legal size spec
    OctetString (4)                 // legal exact size
    OctetString (-1 | 1)            // illegal negative size
    OctetString (5 | 0)             // illegal ordering
    OctetString (1 | 1..10)         // illegal overlapping

3.2. Pointer

 The Pointer base type represents values that reference class
 instances, attributes of class instances, or arbitrary identities.
 The only values of the Pointer type that can be present in a module
 can refer to identities.  They are denoted as identifiers of the
 concerned identities.
 When defining a type derived (directly or indirectly) from the
 Pointer base type, the values may be restricted to a specific class,
 attribute or identity, and all (directly or indirectly) derived items
 thereof by appending the identifier of the appropriate construct
 enclosed in parenthesis.
 Value Examples:
    null                          // legal identity name
    snmpUDPDomain                 // legal identity name
 Restriction Examples:
    Pointer (snmpTransportDomain) // legal restriction

3.3. ObjectIdentifier

 The ObjectIdentifier base type represents administratively assigned
 names for use with SNMP and COPS-PR.  This type SHOULD NOT be used in
 protocol independent SMIng modules.  It is meant to be used in SNMP
 and COPS-PR mappings of attributes of type Pointer (Section 3.2).

Strauss & Schoenwaelder Experimental [Page 9] RFC 3780 SMIng May 2004

 Values of this type may be denoted as a sequence of numerical non-
 negative sub-identifier values in which each MUST NOT exceed 2^32-1
 (4294967295).  Sub-identifiers may be denoted in decimal or `0x'-
 prefixed hexadecimal.  They are separated by single dots and without
 any intermediate white space.  Alternatively (and preferred in most
 cases), the first element may be a previously defined or imported
 lower-case identifier, representing a static object identifier
 prefix.
 Although the number of sub-identifiers in SMIng object identifiers is
 not limited, module designers should realize that there may be
 implementations that stick with the SMIv1/v2 limit of 128 sub-
 identifiers.
 Object identifier derived types cannot be restricted in any way.
 Value Examples:
    1.3.6.1                     // legal numerical oid
    mib-2.1                     // legal oid with identifier prefix
    internet.4.1.0x0627.0x01    // legal oid with hex subids
    iso.-1                      // illegal negative subid
    iso.org.6                   // illegal non-heading identifier
    IF-MIB::ifNumber.0          // legal fully qualified instance oid

3.4. Integer32

 The Integer32 base type represents integer values between
 -2^31 (-2147483648) and 2^31-1 (2147483647).
 Values of type Integer32 may be denoted as decimal or hexadecimal
 numbers, where only decimal numbers can be negative.  Decimal numbers
 other than zero MUST NOT have leading zero digits.  Hexadecimal
 numbers are prefixed by `0x' and MUST have an even number of at least
 two hexadecimal digits, where letters MAY be upper-case, but lower-
 case characters are RECOMMENDED.
 When defining a type derived (directly or indirectly) from the
 Integer32 base type, the set of possible values may be restricted by
 appending a list of ranges or explicit values, separated by pipe `|'
 characters, and the whole list enclosed in parenthesis.  A range
 consists of a lower bound, two consecutive dots `..', and an upper
 bound.  Each value can be given in decimal or `0x'-prefixed
 hexadecimal notation.  Hexadecimal numbers must have an even number
 of at least two digits.  If multiple values or ranges are given they
 all MUST be disjoint and MUST be in ascending order.  If a value
 restriction is applied to an already restricted type, the new
 restriction MUST be equal or more limiting, that is raising the lower

Strauss & Schoenwaelder Experimental [Page 10] RFC 3780 SMIng May 2004

 bounds, reducing the upper bounds, removing explicit values or
 ranges, or splitting ranges into multiple ranges with intermediate
 gaps.
 Value Examples:
    015                         // illegal leading zero
    -123                        // legal negative value
    - 1                         // illegal intermediate space
    0xabc                       // illegal hexadecimal value length
    -0xff                       // illegal sign on hex value
    0x80000000                  // illegal value, too large
    0xf00f                      // legal hexadecimal value
 Restriction Examples:
    Integer32 (0 | 5..10)       // legal range spec
    Integer32 (5..10 | 2..3)    // illegal ordering
    Integer32 (4..8 | 5..10)    // illegal overlapping

3.5. Integer64

 The Integer64 base type represents integer values between
 -2^63 (-9223372036854775808) and 2^63-1 (9223372036854775807).
 Values of type Integer64 may be denoted as decimal or hexadecimal
 numbers, where only decimal numbers can be negative.  Decimal numbers
 other than zero MUST NOT have leading zero digits.  Hexadecimal
 numbers are prefixed by `0x' and MUST have an even number of
 hexadecimal digits, where letters MAY be upper-case, but lower-case
 characters are RECOMMENDED.
 When defining a type derived (directly or indirectly) from the
 Integer64 base type, the set of possible values may be restricted by
 appending a list of ranges or explicit values, separated by pipe `|'
 characters, with the whole list enclosed in parenthesis.  A range
 consists of a lower bound, two consecutive dots `..', and an upper
 bound.  Each value can be given in decimal or `0x'-prefixed
 hexadecimal notation.  Hexadecimal numbers must have an even number
 of at least two digits.  If multiple values or ranges are given, they
 all MUST be disjoint and MUST be in ascending order.  If a value
 restriction is applied to an already restricted type, the new
 restriction MUST be equal or more limiting, that is raising the lower
 bounds, reducing the upper bounds, removing explicit values or
 ranges, or splitting ranges into multiple ranges with intermediate
 gaps.

Strauss & Schoenwaelder Experimental [Page 11] RFC 3780 SMIng May 2004

 Value Examples:
    015                         // illegal leading zero
    -123                        // legal negative value
    - 1                         // illegal intermediate space
    0xabc                       // illegal hexadecimal value length
    -0xff                       // illegal sign on hex value
    0x80000000                  // legal value
 Restriction Examples:
    Integer64 (0 | 5..10)       // legal range spec
    Integer64 (5..10 | 2..3)    // illegal ordering
    Integer64 (4..8 | 5..10)    // illegal overlapping

3.6. Unsigned32

 The Unsigned32 base type represents positive integer values between 0
 and 2^32-1 (4294967295).
 Values of type Unsigned32 may be denoted as decimal or hexadecimal
 numbers.  Decimal numbers other than zero MUST NOT have leading zero
 digits.  Hexadecimal numbers are prefixed by `0x' and MUST have an
 even number of hexadecimal digits, where letters MAY be upper-case,
 but lower-case characters are RECOMMENDED.
 When defining a type derived (directly or indirectly) from the
 Unsigned32 base type, the set of possible values may be restricted by
 appending a list of ranges or explicit values, separated by pipe `|'
 characters, with the whole list enclosed in parenthesis.  A range
 consists of a lower bound, two consecutive dots `..', and an upper
 bound.  Each value can be given in decimal or `0x'-prefixed
 hexadecimal notation.  Hexadecimal numbers must have an even number
 of at least two digits.  If multiple values or ranges are given, they
 all MUST be disjoint and MUST be in ascending order.  If a value
 restriction is applied to an already restricted type, the new
 restriction MUST be equal or more limiting, that is raising the lower
 bounds, reducing the upper bounds, removing explicit values or
 ranges, or splitting ranges into multiple ranges with intermediate
 gaps.
 Value Examples:
    015                         // illegal leading zero
    -123                        // illegal negative value
    0xabc                       // illegal hexadecimal value length
    0x80000000                  // legal hexadecimal value
    0x8080000000                // illegal value, too large

Strauss & Schoenwaelder Experimental [Page 12] RFC 3780 SMIng May 2004

 Restriction Examples:
    Unsigned32 (0 | 5..10)       // legal range spec
    Unsigned32 (5..10 | 2..3)    // illegal ordering
    Unsigned32 (4..8 | 5..10)    // illegal overlapping

3.7. Unsigned64

 The Unsigned64 base type represents positive integer values between 0
 and 2^64-1 (18446744073709551615).
 Values of type Unsigned64 may be denoted as decimal or hexadecimal
 numbers.  Decimal numbers other than zero MUST NOT have leading zero
 digits.  Hexadecimal numbers are prefixed by `0x' and MUST have an
 even number of hexadecimal digits, where letters MAY be upper-case,
 but lower-case characters are RECOMMENDED.
 When defining a type derived (directly or indirectly) from the
 Unsigned64 base type, the set of possible values may be restricted by
 appending a list of ranges or explicit values, separated by pipe `|'
 characters, with the whole list enclosed in parenthesis.  A range
 consists of a lower bound, two consecutive dots `..', and an upper
 bound.  Each value can be given in decimal or `0x'-prefixed
 hexadecimal notation.  Hexadecimal numbers must have an even number
 of at least two digits.  If multiple values or ranges are given, they
 all MUST be disjoint and MUST be in ascending order.  If a value
 restriction is applied to an already restricted type, the new
 restriction MUST be equal or more limiting, that is raising the lower
 bounds, reducing the upper bounds, removing explicit values or
 ranges, or splitting ranges into multiple ranges with intermediate
 gaps.
 Value Examples:
    015                         // illegal leading zero
    -123                        // illegal negative value
    0xabc                       // illegal hexadecimal value length
    0x8080000000                // legal hexadecimal value
 Restriction Examples:
    Unsigned64 (1..10000000000) // legal range spec
    Unsigned64 (5..10 | 2..3)   // illegal ordering

3.8. Float32

 The Float32 base type represents floating point values of single
 precision as described by [IEEE754].

Strauss & Schoenwaelder Experimental [Page 13] RFC 3780 SMIng May 2004

 Values of type Float32 may be denoted as a decimal fraction with an
 optional exponent, as known from many programming languages.  See the
 grammar rule `floatValue' of Appendix B for the detailed syntax.
 Special values are `snan' (signalling Not-a-Number), `qnan' (quiet
 Not-a-Number), `neginf' (negative infinity), and `posinf' (positive
 infinity).  Note that -0.0 and +0.0 are different floating point
 values.  0.0 is equal to +0.0.
 When defining a type derived (directly or indirectly) from the
 Float32 base type, the set of possible values may be restricted by
 appending a list of ranges or explicit values, separated by pipe `|'
 characters, with the whole list enclosed in parenthesis.  A range
 consists of a lower bound, two consecutive dots `..', and an upper
 bound.  If multiple values or ranges are given, they all MUST be
 disjoint and MUST be in ascending order.  If a value restriction is
 applied to an already restricted type, the new restriction MUST be
 equal or more limiting, that is raising the lower bounds, reducing
 the upper bounds, removing explicit values or ranges, or splitting
 ranges into multiple ranges with intermediate gaps.  The special
 values `snan', `qnan', `neginf', and `posinf' must be explicitly
 listed in restrictions if they shall be included, where `snan' and
 `qnan' cannot be used in ranges.
 Note that encoding is not subject to this specification.  It has to
 be described by protocols that transport objects of type Float32.
 Note also that most floating point encodings disallow the
 representation of many values that can be written as decimal
 fractions as used in SMIng for human readability.  Therefore,
 explicit values in floating point type restrictions should be handled
 with care.
 Value Examples:
    00.1                       // illegal leading zero
    3.1415                     // legal value
    -2.5E+3                    // legal negative exponential value
 Restriction Examples:
    Float32 (-1.0..1.0)        // legal range spec
    Float32 (1 | 3.3 | 5)      // legal, probably unrepresentable 3.3
    Float32 (neginf..-0.0)     // legal range spec
    Float32 (-10.0..10.0 | 0)  // illegal overlapping

Strauss & Schoenwaelder Experimental [Page 14] RFC 3780 SMIng May 2004

3.9. Float64

 The Float64 base type represents floating point values of double
 precision as described by [IEEE754].
 Values of type Float64 may be denoted as a decimal fraction with an
 optional exponent, as known from many programming languages.  See the
 grammar rule `floatValue' of Appendix B for the detailed syntax.
 Special values are `snan' (signalling Not-a-Number), `qnan' (quiet
 Not-a-Number), `neginf' (negative infinity), and `posinf' (positive
 infinity).  Note that -0.0 and +0.0 are different floating point
 values.  0.0 is equal to +0.0.
 When defining a type derived (directly or indirectly) from the
 Float64 base type, the set of possible values may be restricted by
 appending a list of ranges or explicit values, separated by pipe `|'
 characters, with the whole list enclosed in parenthesis.  A range
 consists of a lower bound, two consecutive dots `..', and an upper
 bound.  If multiple values or ranges are given, they all MUST be
 disjoint and MUST be in ascending order.  If a value restriction is
 applied to an already restricted type, the new restriction MUST be
 equal or more limiting, that is raising the lower bounds, reducing
 the upper bounds, removing explicit values or ranges, or splitting
 ranges into multiple ranges with intermediate gaps.  The special
 values `snan', `qnan', `neginf', and `posinf' must be explicitly
 listed in restrictions if they shall be included, where `snan' and
 `qnan' cannot be used in ranges.
 Note that encoding is not subject to this specification.  It has to
 be described by protocols that transport objects of type Float64.
 Note also that most floating point encodings disallow the
 representation of many values that can be written as decimal
 fractions as used in SMIng for human readability.  Therefore,
 explicit values in floating point type restrictions should be handled
 with care.
 Value Examples:
    00.1                       // illegal leading zero
    3.1415                     // legal value
    -2.5E+3                    // legal negative exponential value
 Restriction Examples:
    Float64 (-1.0..1.0)        // legal range spec
    Float64 (1 | 3.3 | 5)      // legal, probably unrepresentable 3.3
    Float64 (neginf..-0.0)     // legal range spec
    Float64 (-10.0..10.0 | 0)  // illegal overlapping

Strauss & Schoenwaelder Experimental [Page 15] RFC 3780 SMIng May 2004

3.10. Float128

 The Float128 base type represents floating point values of quadruple
 precision as described by [IEEE754].
 Values of type Float128 may be denoted as a decimal fraction with an
 optional exponent, as known from many programming languages.  See the
 grammar rule `floatValue' of Appendix B for the detailed syntax.
 Special values are `snan' (signalling Not-a-Number), `qnan' (quiet
 Not-a-Number), `neginf' (negative infinity), and `posinf' (positive
 infinity).  Note that -0.0 and +0.0 are different floating point
 values.  0.0 is equal to +0.0.
 When defining a type derived (directly or indirectly) from the
 Float128 base type, the set of possible values may be restricted by
 appending a list of ranges or explicit values, separated by pipe `|'
 characters, with the whole list enclosed in parenthesis.  A range
 consists of a lower bound, two consecutive dots `..', and an upper
 bound.  If multiple values or ranges are given, they all MUST be
 disjoint and MUST be in ascending order.  If a value restriction is
 applied to an already restricted type, the new restriction MUST be
 equal or more limiting, that is raising the lower bounds, reducing
 the upper bounds, removing explicit values or ranges, or splitting
 ranges into multiple ranges with intermediate gaps.  The special
 values `snan', `qnan', `neginf', and `posinf' must be explicitly
 listed in restrictions if they shall be included, where `snan' and
 `qnan' cannot be used in ranges.
 Note that encoding is not subject to this specification.  It has to
 be described by protocols that transport objects of type Float128.
 Note also that most floating point encodings disallow the
 representation of many values that can be written as decimal
 fractions as used in SMIng for human readability.  Therefore,
 explicit values in floating point type restrictions should be handled
 with care.
 Value Examples:
    00.1                       // illegal leading zero
    3.1415                     // legal value
    -2.5E+3                    // legal negative exponential value
 Restriction Examples:
    Float128 (-1.0..1.0)        // legal range spec
    Float128 (1 | 3.3 | 5)      // legal, probably unrepresentable 3.3
    Float128 (neginf..-0.0)     // legal range spec
    Float128 (-10.0..10.0 | 0)  // illegal overlapping

Strauss & Schoenwaelder Experimental [Page 16] RFC 3780 SMIng May 2004

3.11. Enumeration

 The Enumeration base type represents values from a set of integers in
 the range between -2^31 (-2147483648) and 2^31-1 (2147483647), where
 each value has an assigned name.  The list of those named numbers has
 to be comma-separated, enclosed in parenthesis, and appended to the
 `Enumeration' keyword.  Each named number is denoted by its lower-
 case identifier followed by the assigned integer value, denoted as a
 decimal or `0x'-prefixed hexadecimal number, enclosed in parenthesis.
 Hexadecimal numbers must have an even number of at least two digits.
 Every name and every number in an enumeration type MUST be unique.
 It is RECOMMENDED that values be positive, start at 1, and be
 numbered contiguously.  All named numbers MUST be given in ascending
 order.
 Values of enumeration types may be denoted as decimal or `0x'-
 prefixed hexadecimal numbers or preferably as their assigned names.
 Hexadecimal numbers must have an even number of at least two digits.
 When types are derived (directly or indirectly) from an enumeration
 type, the set of named numbers may be equal or restricted by removing
 one or more named numbers, but no named numbers may be added or
 changed regarding its name, value, or both.
 Type and Value Examples:
 Enumeration (up(1), down(2), testing(3))
 Enumeration (down(2), up(1)) // illegal order
 0                            // legal (though not recommended) value
 up                           // legal value given by name
 2                            // legal value given by number

3.12. Bits

 The Bits base type represents bit sets.  That is, a Bits value is a
 set of flags identified by small integer numbers starting at 0.  Each
 bit number has an assigned name.  The list of those named numbers has
 to be comma-separated, enclosed in parenthesis, and appended to the
 `Bits' keyword.  Each named number is denoted by its lower-case
 identifier followed by the assigned integer value, denoted as a
 decimal or `0x'-prefixed hexadecimal number, enclosed in parenthesis.
 Hexadecimal numbers must have an even number of at least two digits.
 Every name and every number in a bits type MUST be unique.  It is
 RECOMMENDED that numbers start at 0 and be numbered contiguously.
 Negative numbers are forbidden.  All named numbers MUST be given in
 ascending order.

Strauss & Schoenwaelder Experimental [Page 17] RFC 3780 SMIng May 2004

 Values of bits types may be denoted as a comma-separated list of
 decimal or `0x'-prefixed hexadecimal numbers or preferably their
 assigned names enclosed in parenthesis.  Hexadecimal numbers must
 have an even number of at least two digits.  There MUST NOT be any
 element (by name or number) listed more than once.  Elements MUST be
 listed in ascending order.
 When defining a type derived (directly or indirectly) from a bits
 type, the set of named numbers may be restricted by removing one or
 more named numbers, but no named numbers may be added or changed
 regarding its name, value, or both.
 Type and Value Examples:
    Bits (readable(0), writable(1), executable(2))
    Bits (writable(1), readable(0) // illegal order
    ()                          // legal empty value
    (readable, writable, 2)     // legal value
    (0, readable, executable)   // illegal, readable(0) appears twice
    (writable, 4)               // illegal, element 4 out of range

3.13. Display Formats

 Attribute and type definitions allow the specification of a format to
 be used when a value of that attribute or an attribute of that type
 is displayed.  Format specifications are represented as textual data.
 When the attribute or type has an underlying base type of Integer32,
 Integer64, Unsigned32, or Unsigned64, the format consists of an
 integer-format specification containing two parts.  The first part is
 a single character suggesting a display format, either: `x' for
 hexadecimal, `d' for decimal, `o' for octal, or `b' for binary.  For
 all types, when rendering the value, leading zeros are omitted, and
 for negative values, a minus sign is rendered immediately before the
 digits.  The second part is always omitted for `x', `o', and `b', and
 need not be present for `d'.  If present, the second part starts with
 a hyphen and is followed by a decimal number, which defines the
 implied decimal point when rendering the value.  For example `d-2'
 suggests that a value of 1234 be rendered as `12.34'.
 When the attribute or type has an underlying base type of
 OctetString, the format consists of one or more octet-format
 specifications.  Each specification consists of five parts, with each
 part using and removing zero or more of the next octets from the

Strauss & Schoenwaelder Experimental [Page 18] RFC 3780 SMIng May 2004

 value and producing the next zero or more characters to be displayed.
 The octets within the value are processed in order of significance,
 most significant first.
 The five parts of a octet-format specification are:
 1. The (optional) repeat indicator.  If present, this part is a `*',
    and indicates that the current octet of the value is to be used as
    the repeat count.  The repeat count is an unsigned integer (which
    may be zero) specifying how many times the remainder of this
    octet-format specification should be successively applied.  If the
    repeat indicator is not present, the repeat count is one.
 2. The octet length: one or more decimal digits specifying the number
    of octets of the value to be used and formatted by this octet-
    specification.  Note that the octet length can be zero.  If less
    than this number of octets remain in the value, then the lesser
    number of octets are used.
 3. The display format, either: `x' for hexadecimal, `d' for decimal,
    `o' for octal, `a' for ASCII, or `t' for UTF-8 [RFC3629].  If the
    octet length part is greater than one, and the display format part
    refers to a numeric format, then network byte-ordering (big-endian
    encoding) is used to interpret the octets in the value.  The
    octets processed by the `t' display format do not necessarily form
    an integral number of UTF-8 characters.  Trailing octets which do
    not form a valid UTF-8 encoded character are discarded.
 4. The (optional) display separator character.  If present, this part
    is a single character produced for display after each application
    of this octet-specification; however, this character is not
    produced for display if it would be immediately followed by the
    display of the repeat terminator character for this octet
    specification.  This character can be any character other than a
    decimal digit and a `*'.
 5. The (optional) repeat terminator character, which can be present
    only if the display separator character is present and this octet
    specification begins with a repeat indicator.  If present, this
    part is a single character produced after all the zero or more
    repeated applications (as given by the repeat count) of this octet
    specification.  This character can be any character other than a
    decimal digit and a `*'.
 Output of a display separator character or a repeat terminator
 character is suppressed if it would occur as the last character of
 the display.

Strauss & Schoenwaelder Experimental [Page 19] RFC 3780 SMIng May 2004

 If the octets of the value are exhausted before all the octet format
 specifications have been used, then the excess specifications are
 ignored.  If additional octets remain in the value after interpreting
 all the octet format specifications, then the last octet format
 specification is re-interpreted to process the additional octets,
 until no octets remain in the value.
 Note that for some types, no format specifications are defined.  For
 derived types and attributes that are based on such types, format
 specifications SHOULD be omitted.  Implementations MUST ignore format
 specifications they cannot interpret.  Also note that the SMIng
 grammar (Appendix B) does not specify the syntax of format
 specifications.
 Display Format Examples:
    Base Type   Format              Example Value    Rendered Value
    ----------- ------------------- ---------------- -----------------
    OctetString 255a                "Hello World."   Hello World.
    OctetString 1x:                 "Hello!"         48:65:6c:6c:6f:21
    OctetString 1d:1d:1d.1d,1a1d:1d 0x0d1e0f002d0400 13:30:15.0,-4:0
    OctetString 1d.1d.1d.1d/2d      0x0a0000010400   10.0.0.1/1024
    OctetString *1x:/1x:            0x02aabbccddee   aa:bb/cc:dd:ee
    Integer32   d-2                 1234             12.34

4. The SMIng File Structure

 The topmost container of SMIng information is a file.  An SMIng file
 may contain zero, one or more modules.  It is RECOMMENDED that
 modules be stored into separate files by their module names, where
 possible.  However, for dedicated purposes, it may be reasonable to
 collect several modules in a single file.
 The top level SMIng construct is the `module' statement (Section 5)
 that defines a single SMIng module.  A module contains a sequence of
 sections in an obligatory order with different kinds of definitions.
 Whether these sections contain statements or remain empty mainly
 depends on the purpose of the module.

4.1. Comments

 Comments can be included at any position in an SMIng file, except
 between the characters of a single token like those of a quoted
 string.  However, it is RECOMMENDED that all substantive descriptions
 be placed within an appropriate description clause, so that the
 information is available to SMIng parsers.

Strauss & Schoenwaelder Experimental [Page 20] RFC 3780 SMIng May 2004

 Comments commence with a pair of adjacent slashes `//' and end at the
 end of the line.

4.2. Textual Data

 Some statements, namely `organization', `contact', `description',
 `reference', `abnf', `format', and `units', get a textual argument.
 This text, as well as representations of OctetString values, have to
 be enclosed in double quotes.  They may contain arbitrary characters
 with the following exceptional encoding rules:
 A backslash character introduces a special character, which depends
 on the character that immediately follows the backslash:
    \n      new line
    \t      a tab character
    \"      a double quote
    \\      a single backslash
 If the text contains a line break followed by whitespace which is
 used to indent the text according to the layout in the SMIng file,
 this prefixing whitespace is stripped from the text.

4.3. Statements and Arguments

 SMIng has a very small set of basic grammar rules based on the
 concept of statements.  Each statement starts with a lower-case
 keyword identifying the statement, followed by a number (possibly
 zero) of arguments.  An argument may be quoted text, an identifier, a
 value of any base type, a list of identifiers enclosed in parenthesis
 `( )', or a statement block enclosed in curly braces `{ }'.  Since
 statement blocks are valid arguments, it is possible to nest
 statement sequences.  Each statement is terminated by a semicolon
 `;'.
 The core set of statements may be extended using the SMIng
 `extension' statement.  See Sections 6 and 11 for details.
 At places where a statement is expected, but an unknown lower-case
 word is read, those statements MUST be skipped up to the proper
 semicolon, including nested statement blocks.

5. The module Statement

 The `module' statement is used as a container of all definitions of a
 single SMIng module.  It gets two arguments: an upper-case module
 name and a statement block that contains mandatory and optional
 statements and sections of statements in an obligatory order:

Strauss & Schoenwaelder Experimental [Page 21] RFC 3780 SMIng May 2004

       module <MODULE-NAME> {
           <optional import statements>
           <organization statement>
           <contact statement>
           <description statement>
           <optional reference statement>
           <at least one revision statement>
           <optional extension statements>
           <optional typedef statements>
           <optional identity statements>
           <optional class statements>
       };
 The optional `import' statements (Section 5.1) are followed by the
 mandatory `organization' (Section 5.2), `contact' (Section 5.3), and
 `description' (Section 5.4) statements and the optional `reference'
 statement (Section 5.5), which in turn are followed by at least one
 mandatory `revision' statement (Section 5.6).  The part up to this
 point defines the module's meta information, i.e., information that
 describes the whole module but does not define any items used by
 applications in the first instance.  This part of a module is
 followed by its main definitions, namely SMIng extensions (Section
 6), derived types (Section 7), identities (Section 8), and classes
 (Section 9).
 See the `moduleStatement' rule of the SMIng grammar (Appendix B) for
 the formal syntax of the `module' statement.

5.1. The module's import Statement

 The optional module's `import' statement is used to import
 identifiers from external modules into the local module's namespace.
 It gets two arguments: the name of the external module and a comma-
 separated list of one or more identifiers to be imported enclosed in
 parenthesis.
 Multiple `import' statements for the same module but with disjoint
 lists of identifiers are allowed, though NOT RECOMMENDED.  The same
 identifier from the same module MUST NOT be imported multiple times.
 To import identifiers with the same name from different modules might
 be necessary and is allowed.  To distinguish

Strauss & Schoenwaelder Experimental [Page 22] RFC 3780 SMIng May 2004

 them in the local module, they have to be referred by qualified
 names.  Importing identifiers not used in the local module is NOT
 RECOMMENDED.
 See the `importStatement' rule of the SMIng grammar (Appendix B) for
 the formal syntax of the `import' statement.

5.2. The module's organization Statement

 The module's `organization' statement, which must be present, gets
 one argument which is used to specify a textual description of the
 organization(s) under whose auspices this module was developed.

5.3. The module's contact Statement

 The module's `contact' statement, which must be present, gets one
 argument which is used to specify the name, postal address, telephone
 number, and electronic mail address of the person to whom technical
 queries concerning this module should be sent.

5.4. The module's description Statement

 The module's `description' statement, which must be present, gets one
 argument which is used to specify a high-level textual description of
 the contents of this module.

5.5. The module's reference Statement

 The module's `reference' statement, which need not be present, gets
 one argument which is used to specify a textual cross-reference to
 some other document, either another module which defines related
 management information, or some other document which provides
 additional information relevant to this module.

5.6. The module's revision Statement

 The module's `revision' statement is repeatedly used to specify the
 editorial revisions of the module, including the initial revision.
 It gets one argument which is a statement block that holds detailed
 information in an obligatory order.  A module MUST have at least one
 initial `revision' statement.  For every editorial change, a new one
 MUST be added in front of the revisions sequence, so that all
 revisions are in reverse chronological order.
 See the `revisionStatement' rule of the SMIng grammar (Appendix B)
 for the formal syntax of the `revision' statement.

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5.6.1. The revision's date Statement

 The revision's `date' statement, which must be present, gets one
 argument which is used to specify the date and time of the revision
 in the format `YYYY-MM-DD HH:MM' or `YYYY-MM-DD' which implies the
 time `00:00'.  The time is always given in UTC.
 See the `date' rule of the SMIng grammar (Appendix B) for the formal
 syntax of the revision's `date' statement.

5.6.2. The revision's description Statement

 The revision's `description' statement, which must be present, gets
 one argument which is used to specify a high-level textual
 description of the revision.

5.7. Usage Example

 Consider how a skeletal module might be constructed:
 module ACME-MIB {
   import NMRG-SMING (DisplayString);
   organization
             "IRTF Network Management Research Group (NMRG)";
   contact   "IRTF Network Management Research Group (NMRG)
              http://www.ibr.cs.tu-bs.de/projects/nmrg/
              Joe L. User
              ACME, Inc.
              42 Anywhere Drive
              Nowhere, CA 95134
              USA
              Phone: +1 800 555 0815
              EMail: joe@acme.example.com";
   description
             "The module for entities implementing the ACME protocol.
              Copyright (C) The Internet Society (2004).
              All Rights Reserved.
              This version of this MIB module is part of RFC 3780,
              see the RFC itself for legal notices.";

Strauss & Schoenwaelder Experimental [Page 24] RFC 3780 SMIng May 2004

   revision {
     date            "2003-12-16";
     description
             "Initial revision, published as RFC 3780.";
   };
   // ... further definitions ...
 }; // end of module ACME-MIB.

6. The extension Statement

 The `extension' statement defines new statements to be used in the
 local module following this extension statement definition or in
 external modules that may import this extension statement definition.
 The `extension' statement gets two arguments: a lower-case extension
 statement identifier and a statement block that holds detailed
 extension information in an obligatory order.
 Extension statement identifiers SHOULD NOT contain any upper-case
 characters.
 Note that the SMIng extension feature does not allow the formal
 specification of the context, or argument syntax and semantics of an
 extension.  Its only purpose is to declare the existence of an
 extension and to allow a unique reference to an extension.  See
 Section 11 for detailed information on extensions and [RFC3781] for
 mappings of SMIng definitions to SNMP, which is formally defined as
 an extension.
 See the `extensionStatement' rule of the SMIng grammar (Appendix B)
 for the formal syntax of the `extension' statement.

6.1. The extension's status Statement

 The extension's `status' statement, which must be present, gets one
 argument which is used to specify whether this extension definition
 is current or historic.  The value `current' means that the
 definition is current and valid.  The value `obsolete' means the
 definition is obsolete and should not be implemented and/or can be
 removed if previously implemented.  While the value `deprecated' also
 indicates an obsolete definition, it permits new/continued
 implementation in order to foster interoperability with older/
 existing implementations.

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6.2. The extension's description Statement

 The extension's `description' statement, which must be present, gets
 one argument which is used to specify a high-level textual
 description of the extension statement.
 It is RECOMMENDED that information on the extension's context, its
 semantics, and implementation conditions be included.  See also
 Section 11.

6.3. The extension's reference Statement

 The extension's `reference' statement, which need not be present,
 gets one argument which is used to specify a textual cross-reference
 to some other document, either another module which defines related
 extension definitions, or some other document which provides
 additional information relevant to this extension.

6.4. The extension's abnf Statement

 The extension's `abnf' statement, which need not be present, gets one
 argument which is used to specify a formal ABNF [RFC2234] grammar
 definition of the extension.  This grammar can reference rule names
 from the core SMIng grammar (Appendix B).
 Note that the `abnf' statement should contain only pure ABNF and no
 additional text, though comments prefixed by a semicolon are allowed
 but should probably be moved to the description statement.  Note that
 double quotes within the ABNF grammar have to be represented as `\"'
 according to Section 4.2.

6.5. Usage Example

 extension severity {
   status  current;
   description
          "The optional severity extension statement can only
           be applied to the statement block of an SMIng class'
           event definition. If it is present it denotes the
           severity level of the event in a range from 0
           (emergency) to 7 (debug).";
   abnf
          "severityStatement = severityKeyword sep number optsep \";\"
           severityKeyword   = \"severity\"";
 };

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7. The typedef Statement

 The `typedef' statement defines new data types to be used in the
 local module or in external modules.  It gets two arguments:  an
 upper-case type identifier and a statement block that holds detailed
 type information in an obligatory order.
 Type identifiers SHOULD NOT consist of all upper-case characters and
 SHOULD NOT contain hyphens.
 See the `typedefStatement' rule of the SMIng grammar (Appendix B) for
 the formal syntax of the `typedef' statement.

7.1. The typedef's type Statement

 The typedef's `type' statement, which must be present, gets one
 argument which is used to specify the type from which this type is
 derived.  Optionally, type restrictions may be applied to the new
 type by appending subtyping information according to the rules of the
 base type.  See Section 3 for SMIng base types and their type
 restrictions.

7.2. The typedef's default Statement

 The typedef's `default' statement, which need not be present, gets
 one argument which is used to specify an acceptable default value for
 attributes of this type.  A default value may be used when an
 attribute instance is created.  That is, the value is a "hint" to
 implementors.
 The value of the `default' statement must, of course, correspond to
 the (probably restricted) type specified in the typedef's `type'
 statement.
 The default value of a type may be overwritten by a default value of
 an attribute of this type.
 Note that for some types, default values make no sense.

7.3. The typedef's format Statement

 The typedef's `format' statement, which need not be present, gets one
 argument which is used to give a hint as to how the value of an
 instance of an attribute of this type might be displayed.  See
 Section 3.13 for a description of format specifications.

Strauss & Schoenwaelder Experimental [Page 27] RFC 3780 SMIng May 2004

 If no format is specified, it is inherited from the type given in the
 `type' statement.  On the other hand, the format specification of a
 type may be semantically refined by a format specification of an
 attribute of this type.

7.4. The typedef's units Statement

 The typedef's `units' statement, which need not be present, gets one
 argument which is used to specify a textual definition of the units
 associated with attributes of this type.
 If no units are specified, they are inherited from the type given in
 the `type' statement.  On the other hand, the units specification of
 a type may be semantically refined by a units specification of an
 attribute of this type.
 The units specification has to be appropriate for values displayed
 according to the typedef's format specification, if present.  For
 example, if the type defines frequency values of type Unsigned64
 measured in thousands of Hertz, the format specification should be
 `d-3' and the units specification should be `Hertz' or `Hz'.  If the
 format specification would be omitted, the units specification should
 be `Milli-Hertz' or `mHz'.  Authors of SMIng modules should pay
 attention to keep format and units specifications in sync.
 Application implementors MUST NOT implement units specifications
 without implementing format specifications.

7.5. The typedef's status Statement

 The typedef's `status' statement, which must be present, gets one
 argument which is used to specify whether this type definition is
 current or historic.  The value `current' means that the definition
 is current and valid.  The value `obsolete' means the definition is
 obsolete and should not be implemented and/or can be removed if
 previously implemented.  While the value `deprecated' also indicates
 an obsolete definition, it permits new/continued implementation in
 order to foster interoperability with older/existing implementations.
 Derived types SHOULD NOT be defined as `current' if their underlying
 type is `deprecated' or `obsolete'.  Similarly, they SHOULD NOT be
 defined as `deprecated' if their underlying type is `obsolete'.
 Nevertheless, subsequent revisions of the underlying type cannot be
 avoided, but SHOULD be taken into account in subsequent revisions of
 the local module.

Strauss & Schoenwaelder Experimental [Page 28] RFC 3780 SMIng May 2004

7.6. The typedef's description Statement

 The typedef's `description' statement, which must be present, gets
 one argument which is used to specify a high-level textual
 description of the newly defined type.
 It is RECOMMENDED that all semantic definitions necessary for
 implementation, and to embody any information which would otherwise
 be communicated in any commentary annotations associated with this
 type definition be included.

7.7. The typedef's reference Statement

 The typedef's `reference' statement, which need not be present, gets
 one argument which is used to specify a textual cross-reference to
 some other document, either another module which defines related type
 definitions, or some other document which provides additional
 information relevant to this type definition.

7.8. Usage Examples

 typedef RptrOperStatus {
   type            Enumeration (other(1), ok(2), rptrFailure(3),
                                groupFailure(4), portFailure(5),
                                generalFailure(6));
   default         other;       // undefined by default.
   status          deprecated;
   description
           "A type to indicate the operational state
            of a repeater.";
   reference
           "[IEEE 802.3 Mgt], 30.4.1.1.5, aRepeaterHealthState.";
 };
 typedef SnmpTransportDomain {
   type            Pointer (snmpTransportDomain);
   status          current;
   description
           "A pointer to an SNMP transport domain identity.";
 };
 typedef DateAndTime {
   type            OctetString (8 | 11);
   format          "2d-1d-1d,1d:1d:1d.1d,1a1d:1d";
   status          current;
   description
           "A date-time specification.
            ...

Strauss & Schoenwaelder Experimental [Page 29] RFC 3780 SMIng May 2004

            Note that if only local time is known, then timezone
            information (fields 8-10) is not present.";
   reference
           "RFC 2579, SNMPv2-TC.DateAndTime.";
 };
 typedef Frequency {
   type            Unsigned64;
   format          "d-3"
   units           "Hertz";
   status          current;
   description
           "A wide-range frequency specification measured
            in thousands of Hertz.";
 };

8. The identity Statement

 The `identity' statement is used to define a new abstract and untyped
 identity.  Its only purpose is to denote its name, semantics, and
 existence.  An identity can be defined either from scratch or derived
 from a parent identity.  The `identity' statement gets the following
 two arguments: The first argument is a lower-case identity
 identifier.  The second argument is a statement block that holds
 detailed identity information in an obligatory order.
 See the `identityStatement' rule of the SMIng grammar (Appendix B)
 for the formal syntax of the `identity' statement.

8.1. The identity's parent Statement

 The identity's `parent' statement must be present for a derived
 identity and must be absent for an identity defined from scratch.  It
 gets one argument which is used to specify the parent identity from
 which this identity shall be derived.

8.2. The identity's status Statement

 The identity's `status' statement, which must be present, gets one
 argument which is used to specify whether this identity definition is
 current or historic.  The value `current' means that the definition
 is current and valid.  The value `obsolete' means the definition is
 obsolete and should not be implemented and/or can be removed if
 previously implemented.  While the value `deprecated' also indicates
 an obsolete definition, it permits new/continued implementation in
 order to foster interoperability with older/existing implementations.

Strauss & Schoenwaelder Experimental [Page 30] RFC 3780 SMIng May 2004

 Derived identities SHOULD NOT be defined as `current' if their parent
 identity is `deprecated' or `obsolete'.  Similarly, they SHOULD NOT
 be defined as `deprecated' if their parent identity is `obsolete'.
 Nevertheless, subsequent revisions of the parent identity cannot be
 avoided, but SHOULD be taken into account in subsequent revisions of
 the local module.

8.3. The identity' description Statement

 The identity's `description' statement, which must be present, gets
 one argument which is used to specify a high-level textual
 description of the newly defined identity.
 It is RECOMMENDED that all semantic definitions necessary for
 implementation, and to embody any information which would otherwise
 be communicated in any commentary annotations associated with this
 identity definition be included.

8.4. The identity's reference Statement

 The identity's `reference' statement, which need not be present, gets
 one argument which is used to specify a textual cross-reference to
 some other document, either another module which defines related
 identity definitions, or some other document which provides
 additional information relevant to this identity definition.

8.5. Usage Examples

 identity null {
   status  current;
   description
           "An identity used to represent null pointer values.";
 };
 identity snmpTransportDomain {
   status  current;
   description
           "A generic SNMP transport domain identity.";
 };
 identity snmpUDPDomain {
   parent  snmpTransportDomain;
   status  current;
   description
           "The SNMP over UDP transport domain.";
 };

Strauss & Schoenwaelder Experimental [Page 31] RFC 3780 SMIng May 2004

9. The class Statement

 The `class' statement is used to define a new class that represents a
 container of related attributes and events (Section 9.2, Section
 9.4).  A class can be defined either from scratch or derived from a
 parent class.  A derived class inherits all attributes and events of
 the parent class and can be extended by additional attributes and
 events.
 The `class' statement gets the following two arguments: The first
 argument is an upper-case class identifier.  The second argument is a
 statement block that holds detailed class information in an
 obligatory order.
 See the `classStatement' rule of the SMIng grammar (Appendix B) for
 the formal syntax of the `class' statement.

9.1. The class' extends Statement

 The class' `extends' statement must be present for a class derived
 from a parent class and must be absent for a class defined from
 scratch.  It gets one argument which is used to specify the parent
 class from which this class shall be derived.

9.2. The class' attribute Statement

 The class' `attribute' statement, which can be present zero, one or
 multiple times, gets two arguments: the attribute name and a
 statement block that holds detailed attribute information in an
 obligatory order.

9.2.1. The attribute's type Statement

 The attribute's `type' statement must be present.  It gets at least
 one argument which is used to specify the type of the attribute:
 either a type name or a class name.  In case of a type name, it may
 be restricted by a second argument according to the restriction rules
 described in Section 3.

9.2.2. The attribute's access Statement

 The attribute's `access' statement must be present for attributes
 typed by a base type or derived type, and must be absent for
 attributes typed by a class.  It gets one argument which is used to
 specify whether it makes sense to read and/or write an instance of
 the attribute, or to include its value in an event.  This is the
 maximal level of access for the attribute.  This maximal level of
 access is independent of any administrative authorization policy.

Strauss & Schoenwaelder Experimental [Page 32] RFC 3780 SMIng May 2004

 The value `readwrite' indicates that read and write access makes
 sense.  The value `readonly' indicates that read access makes sense,
 but write access is never possible.  The value `eventonly' indicates
 an object which is accessible only via an event.
 These values are ordered, from least to greatest access level:
 `eventonly', `readonly', `readwrite'.

9.2.3. The attribute's default Statement

 The attribute's `default' statement need not be present for
 attributes typed by a base type or derived type, and must be absent
 for attributes typed by a class.  It gets one argument which is used
 to specify an acceptable default value for this attribute.  A default
 value may be used when an attribute instance is created.  That is,
 the value is a "hint" to implementors.
 The value of the `default' statement must, of course, correspond to
 the (probably restricted) type specified in the attribute's `type'
 statement.
 The attribute's default value overrides the default value of the
 underlying type definition if both are present.

9.2.4. The attribute's format Statement

 The attribute's `format' statement need not be present for attributes
 typed by a base type or derived type, and must be absent for
 attributes typed by a class.  It gets one argument which is used to
 give a hint as to how the value of an instance of this attribute
 might be displayed.  See Section 3.13 for a description of format
 specifications.
 The attribute's format specification overrides the format
 specification of the underlying type definition if both are present.

9.2.5. The attribute's units Statement

 The attribute's `units' statement need not be present for attributes
 typed by a base type or derived type, and must be absent for
 attributes typed by a class.  It gets one argument which is used to
 specify a textual definition of the units associated with this
 attribute.
 The attribute's units specification overrides the units specification
 of the underlying type definition if both are present.

Strauss & Schoenwaelder Experimental [Page 33] RFC 3780 SMIng May 2004

 The units specification has to be appropriate for values displayed
 according to the attribute's format specification if present.  For
 example, if the attribute represents a frequency value of type
 Unsigned64 measured in thousands of Hertz, the format specification
 should be `d-3' and the units specification should be `Hertz' or
 `Hz'.  If the format specification would be omitted, the units
 specification should be `Milli-Hertz' or `mHz'.  Authors of SMIng
 modules should pay attention to keep format and units specifications
 of type and attribute definitions in sync.  Application implementors
 MUST NOT implement units specifications without implementing format
 specifications.

9.2.6. The attribute's status Statement

 The attribute's `status' statement must be present.  It gets one
 argument which is used to specify whether this attribute definition
 is current or historic.  The value `current' means that the
 definition is current and valid.  The value `obsolete' means the
 definition is obsolete and should not be implemented and/or can be
 removed if previously implemented.  While the value `deprecated' also
 indicates an obsolete definition, it permits new/continued
 implementation in order to foster interoperability with older/
 existing implementations.
 Attributes SHOULD NOT be defined as `current' if their type or their
 containing class is `deprecated' or `obsolete'.  Similarly, they
 SHOULD NOT be defined as `deprecated' if their type or their
 containing class is `obsolete'.  Nevertheless, subsequent revisions
 of used type definition cannot be avoided, but SHOULD be taken into
 account in subsequent revisions of the local module.

9.2.7. The attribute's description Statement

 The attribute's `description' statement, which must be present, gets
 one argument which is used to specify a high-level textual
 description of this attribute.
 It is RECOMMENDED that all semantic definitions necessary for the
 implementation of this attribute be included.

9.2.8. The attribute's reference Statement

 The attribute's `reference' statement, which need not be present,
 gets one argument which is used to specify a textual cross-reference
 to some other document, either another module which defines related
 attribute definitions, or some other document which provides
 additional information relevant to this attribute definition.

Strauss & Schoenwaelder Experimental [Page 34] RFC 3780 SMIng May 2004

9.3. The class' unique Statement

 The class' `unique' statement, which need not be present, gets one
 argument that specifies a comma-separated list of attributes of this
 class, enclosed in parenthesis.  If present, this list of attributes
 makes up a unique identification of all possible instances of this
 class.  It can be used as a unique key in underlying protocols.
 If the list is empty, the class should be regarded as a scalar class
 with only a single instance.
 If the `unique' statement is not present, the class is not meant to
 be instantiated directly, but to be contained in other classes or the
 parent class of other refining classes.
 If present, the attribute list MUST NOT contain any attribute more
 than once and the attributes should be ordered where appropriate so
 that the attributes that are most significant in most situations
 appear first.

9.4. The class' event Statement

 The class' `event' statement is used to define an event related to an
 instance of this class that can occur asynchronously.  It gets two
 arguments: a lower-case event identifier and a statement block that
 holds detailed information in an obligatory order.
 See the `eventStatement' rule of the SMIng grammar (Appendix B) for
 the formal syntax of the `event' statement.

9.4.1. The event's status Statement

 The event's `status' statement, which must be present, gets one
 argument which is used to specify whether this event definition is
 current or historic.  The value `current' means that the definition
 is current and valid.  The value `obsolete' means the definition is
 obsolete and should not be implemented and/or can be removed if
 previously implemented.  While the value `deprecated' also indicates
 an obsolete definition, it permits new/continued implementation in
 order to foster interoperability with older/existing implementations.

9.4.2. The event's description Statement

 The event's `description' statement, which must be present, gets one
 argument which is used to specify a high-level textual description of
 this event.

Strauss & Schoenwaelder Experimental [Page 35] RFC 3780 SMIng May 2004

 It is RECOMMENDED that all semantic definitions necessary for the
 implementation of this event be included.  In particular, which
 instance of the class is associated with an event of this type SHOULD
 be documented.

9.4.3. The event's reference Statement

 The event's `reference' statement, which need not be present, gets
 one argument which is used to specify a textual cross-reference to
 some other document, either another module which defines related
 event definitions, or some other document which provides additional
 information relevant to this event definition.

9.5. The class' status Statement

 The class' `status' statement, which must be present, gets one
 argument which is used to specify whether this class definition is
 current or historic.  The value `current' means that the definition
 is current and valid.  The value `obsolete' means the definition is
 obsolete and should not be implemented and/or can be removed if
 previously implemented.  While the value `deprecated' also indicates
 an obsolete definition, it permits new/continued implementation in
 order to foster interoperability with older/existing implementations.
 Derived classes SHOULD NOT be defined as `current' if their parent
 class is `deprecated' or `obsolete'.  Similarly, they SHOULD NOT be
 defined as `deprecated' if their parent class is `obsolete'.
 Nevertheless, subsequent revisions of the parent class cannot be
 avoided, but SHOULD be taken into account in subsequent revisions of
 the local module.

9.6. The class' description Statement

 The class' `description' statement, which must be present, gets one
 argument which is used to specify a high-level textual description of
 the newly defined class.
 It is RECOMMENDED that all semantic definitions necessary for
 implementation, and to embody any information which would otherwise
 be communicated in any commentary annotations associated with this
 class definition be included.

Strauss & Schoenwaelder Experimental [Page 36] RFC 3780 SMIng May 2004

9.7. The class' reference Statement

 The class' `reference' statement, which need not be present, gets one
 argument which is used to specify a textual cross-reference to some
 other document, either another module which defines related class
 definitions, or some other document which provides additional
 information relevant to this class definition.

9.8. Usage Example

 Consider how an event might be described that signals a status change
 of an interface:
 class Interface {
   // ...
   attribute speed {
     type        Gauge32;
     access      readonly;
     units       "bps";
     status      current;
     description
          "An estimate of the interface's current bandwidth
           in bits per second.";
   };
   // ...
   attribute adminStatus {
     type        AdminStatus;
     access      readwrite;
     status      current;
     description
          "The desired state of the interface.";
   };
   attribute operStatus {
     type        OperStatus;
     access      readonly;
     status      current;
     description
          "The current operational state of the interface.";
   };
   event linkDown {
     status      current;
     description
             "A linkDown event signifies that the ifOperStatus
              attribute for this interface instance is about to
              enter the down state from some other state (but not
              from the notPresent state).  This other state is
              indicated by the included value of ifOperStatus.";

Strauss & Schoenwaelder Experimental [Page 37] RFC 3780 SMIng May 2004

   };
   status        current;
   description
             "A physical or logical network interface.";
 };

10. Extending a Module

 As experience is gained with a module, it may be desirable to revise
 that module.  However, changes are not allowed if they have any
 potential to cause interoperability problems between an
 implementation using an original specification and an implementation
 using an updated specification(s).
 For any change, some statements near the top of the module MUST be
 updated to include information about the revision: specifically, a
 new `revision' statement (Section 5.6) must be included in front of
 the `revision' statements.  Furthermore, any necessary changes MUST
 be applied to other statements, including the `organization' and
 `contact' statements (Section 5.2, Section 5.3).
 Note that any definition contained in a module is available to be
 imported by any other module, and is referenced in an `import'
 statement via the module name.  Thus, a module name MUST NOT be
 changed.  Specifically, the module name (e.g., `ACME-MIB' in the
 example of Section 5.7) MUST NOT be changed when revising a module
 (except to correct typographical errors), and definitions MUST NOT be
 moved from one module to another.
 Also note that obsolete definitions MUST NOT be removed from modules
 since their identifiers may still be referenced by other modules.
 A definition may be revised in any of the following ways:
 o  In `typedef' statement blocks, a `type' statement containing an
    `Enumeration' or `Bits' type may have new named numbers added.
 o  In `typedef' statement blocks, the value of a `type' statement may
    be replaced by another type if the new type is derived (directly
    or indirectly) from the same base type, has the same set of
    values, and has identical semantics.
 o  In `attribute' statements where the `type' sub-statement specifies
    a class, the class may be replaced by another class if the new
    class is derived (directly or indirectly) from the base class and
    both classes have identical semantics.

Strauss & Schoenwaelder Experimental [Page 38] RFC 3780 SMIng May 2004

 o  In `attribute' statements where the `type' sub-statement specifies
    a base type, a defined type, or an implicitly derived type (i.e.,
    not a class), that type may be replaced by another type if the new
    type is derived (directly or indirectly) from the same base type,
    has the same set of values, and has identical semantics.
 o  In any statement block, a `status' statement value of `current'
    may be revised as `deprecated' or `obsolete'.  Similarly, a
    `status' statement value of `deprecated' may be revised as
    `obsolete'.  When making such a change, the `description'
    statement SHOULD be updated to explain the rationale.
 o  In `typedef' and `attribute' statement blocks, a `default'
    statement may be added or updated.
 o  In `typedef' and `attribute' statement blocks, a `units' statement
    may be added.
 o  A class may be augmented by adding new attributes.
 o  In any statement block, clarifications and additional information
    may be included in the `description' statement.
 o  In any statement block, a `reference' statement may be added or
    updated.
 o  Entirely new extensions, types, identities, and classes may be
    defined, using previously unassigned identifiers.
 Otherwise, if the semantics of any previous definition are changed
 (i.e., if a non-editorial change is made to any definition other than
 those specifically allowed above), then this MUST be achieved by a
 new definition with a new identifier.  In case of a class where the
 semantics of any attributes are changed, the new class can be defined
 by derivation from the old class and refining the changed attributes.
 Note that changing the identifier associated with an existing
 definition is considered a semantic change, as these strings may be
 used in an `import' statement.

11. SMIng Language Extensibility

 While the core SMIng language has a well defined set of statements
 (Section 5 through Section 9.4) that are used to specify those
 aspects of management information commonly regarded as necessary
 without management protocol specific information, there may be

Strauss & Schoenwaelder Experimental [Page 39] RFC 3780 SMIng May 2004

 further information people wish to express.  Describing additional
 information informally in description statements has a disadvantage
 in that this information cannot be parsed by any program.
 SMIng allows modules to include statements that are unknown to a
 parser but fulfil some core grammar rules (Section 4.3).
 Furthermore, additional statements may be defined by the `extension'
 statement (Section 6).  Extensions can be used in the local module or
 in other modules that import the extension.  This has some
 advantages:
 o  A parser can differentiate between statements known as extensions
    and unknown statements.  This enables the parser to complain about
    unknown statements, e.g., due to typos.
 o  If an extension's definition contains a formal ABNF grammar
    definition and a parser is able to interpret this ABNF definition,
    this enables the parser to also complain about the wrong usage of
    an extension.
 o  Since there might be some common need for extensions, there is a
    relatively high probability of extension name collisions
    originated by different organizations, as long as there is no
    standardized extension for that purpose.  The requirement to
    explicitly import extension statements allows those extensions to
    be distinguished.
 o  The supported extensions of an SMIng implementation, e.g., an
    SMIng module compiler, can be clearly expressed.
 The only formal effect of an extension statement definition is to
 declare its existence and status, and optionally its ABNF grammar.
 All additional aspects SHOULD be described in the `description'
 statement:
 o  The detailed semantics of the new statement SHOULD be described.
 o  The contexts in which the new statement can be used SHOULD be
    described, e.g., a new statement may be designed to be used only
    in the statement block of a module, but not in other nested
    statement blocks.  Others may be applicable in multiple contexts.
    In addition, the point in the sequence of an obligatory order of
    other statements, where the new statement may be inserted, might
    be prescribed.
 o  The circumstances that make the new statement mandatory or
    optional SHOULD be described.

Strauss & Schoenwaelder Experimental [Page 40] RFC 3780 SMIng May 2004

 o  The syntax of the new statement SHOULD at least be described
    informally, if not supplied formally in an `abnf' statement.
 o  It might be reasonable to give some suggestions under which
    conditions the implementation of the new statement is adequate and
    how it could be integrated into existent implementations.
 Some possible extension applications are:
 o  The formal mapping of SMIng definitions into the SNMP [RFC3781]
    framework is defined as an SMIng extension.  Other mappings may
    follow in the future.
 o  Inlined annotations to definitions.  For example, a vendor may
    wish to describe additional information to class and attribute
    definitions in private modules.  An example are severity levels of
    events in the statement block of an `event' statement.
 o  Arbitrary annotations to external definitions.  For example, a
    vendor may wish to describe additional information to definitions
    in a "standard" module.  This allows a vendor to implement
    "standard" modules as well as additional private features, without
    redundant module definitions, but on top of "standard" module
    definitions.

12. Security Considerations

 This document defines a language with which to write and read
 descriptions of management information.  The language itself has no
 security impact on the Internet.

13. Acknowledgements

 Since SMIng started as a close successor of SMIv2, some paragraphs
 and phrases are directly taken from the SMIv2 specifications
 [RFC2578], [RFC2579], [RFC2580] written by Jeff Case, Keith
 McCloghrie, David Perkins, Marshall T. Rose, Juergen Schoenwaelder,
 and Steven L. Waldbusser.
 The authors would like to thank all participants of the 7th NMRG
 meeting held in Schloss Kleinheubach from 6-8 September 2000, which
 was a major step towards the current status of this memo, namely
 Heiko Dassow, David Durham, Keith McCloghrie, and Bert Wijnen.
 Furthermore, several discussions within the SMING Working Group
 reflected experience with SMIv2 and influenced this specification at
 some points.

Strauss & Schoenwaelder Experimental [Page 41] RFC 3780 SMIng May 2004

14. References

14.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC2234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
            Specifications: ABNF", RFC 2234, November 1997.

14.2. Informative References

 [RFC3216]  Elliott, C., Harrington, D., Jason, J., Schoenwaelder, J.,
            Strauss, F. and W. Weiss, "SMIng Objectives", RFC 3216,
            December 2001.
 [RFC3781]  Strauss, F. and J. Schoenwaelder, "Next Generation
            Structure of Management Information (SMIng) Mappings to
            the Simple Network Management Protocol (SNMP)", RFC 3781,
            May 2004.
 [RFC2578]  McCloghrie, K., Perkins, D. and J. Schoenwaelder,
            "Structure of Management Information Version 2 (SMIv2)",
            STD 58, RFC 2578, April 1999.
 [RFC2579]  McCloghrie, K., Perkins, D. and J. Schoenwaelder, "Textual
            Conventions for SMIv2", STD 59, RFC 2579, April 1999.
 [RFC2580]  McCloghrie, K., Perkins, D. and J. Schoenwaelder,
            "Conformance Statements for SMIv2", STD 60, RFC 2580,
            April 1999.
 [RFC3159]  McCloghrie, K., Fine, M., Seligson, J., Chan, K., Hahn,
            S., Sahita, R., Smith, A. and F. Reichmeyer, "Structure of
            Policy Provisioning Information (SPPI)", RFC 3159, August
            2001.
 [RFC1155]  Rose, M. and K. McCloghrie, "Structure and Identification
            of Management Information for TCP/IP-based Internets", STD
            16, RFC 1155, May 1990.
 [RFC1212]  Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD
            16, RFC 1212, March 1991.
 [RFC1215]  Rose, M., "A Convention for Defining Traps for use with
            the SNMP", RFC 1215, March 1991.

Strauss & Schoenwaelder Experimental [Page 42] RFC 3780 SMIng May 2004

 [ASN1]     International Organization for Standardization,
            "Specification of Abstract Syntax Notation One (ASN.1)",
            International Standard 8824, December 1987.
 [RFC3411]  Harrington, D., Presuhn, R. and B. Wijnen, "An
            Architecture for Describing Simple Network Management
            Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
            December 2002.
 [IEEE754]  Institute of Electrical and Electronics Engineers, "IEEE
            Standard for Binary Floating-Point Arithmetic", ANSI/IEEE
            Standard 754-1985, August 1985.
 [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
            10646", STD 63, RFC 3629, November 2003.
 [RFC3084]  Chan, K., Seligson, J., Durham, D., Gai, S., McCloghrie,
            K., Herzog, S., Reichmeyer, F., Yavatkar, R. and A. Smith,
            "COPS Usage for Policy Provisioning", RFC 3084, March
            2001.

Strauss & Schoenwaelder Experimental [Page 43] RFC 3780 SMIng May 2004

Appendix A. NMRG-SMING Module

 Most SMIng modules are built on top of the definitions of some
 commonly used derived types.  The definitions of these derived types
 are contained in the NMRG-SMING module which is defined below.  Its
 derived types are generally applicable for modeling all areas of
 management information.  Among these derived types are counter types,
 string types, and date and time related types.
 This module is derived from RFC 2578 [RFC2578] and RFC 2579
 [RFC2579].

module NMRG-SMING {

  organization    "IRTF Network Management Research Group (NMRG)";
  contact         "IRTF Network Management Research Group (NMRG)
                   http://www.ibr.cs.tu-bs.de/projects/nmrg/
                   Frank Strauss
                   TU Braunschweig
                   Muehlenpfordtstrasse 23
                   38106 Braunschweig
                   Germany
                   Phone: +49 531 391 3266
                   EMail: strauss@ibr.cs.tu-bs.de
                   Juergen Schoenwaelder
                   International University Bremen
                   P.O. Box 750 561
                   28725 Bremen
                   Germany
                   Phone: +49 421 200 3587
                   EMail: j.schoenwaelder@iu-bremen.de";
  description     "Core type definitions for SMIng. Several
                   type definitions are SMIng versions of
                   similar SMIv2 or SPPI definitions.
                   Copyright (C) The Internet Society (2004).
                   All Rights Reserved.
                   This version of this module is part of
                   RFC 3780, see the RFC itself for full
                   legal notices.";

Strauss & Schoenwaelder Experimental [Page 44] RFC 3780 SMIng May 2004

  revision {
      date        "2003-12-16";
      description "Initial revision, published as RFC 3780.";
  };
  typedef Gauge32 {
      type        Unsigned32;
      description
         "The Gauge32 type represents a non-negative integer,
          which may increase or decrease, but shall never
          exceed a maximum value, nor fall below a minimum
          value.  The maximum value can not be greater than
          2^32-1 (4294967295 decimal), and the minimum value
          can not be smaller than 0.  The value of a Gauge32
          has its maximum value whenever the information
          being modeled is greater than or equal to its
          maximum value, and has its minimum value whenever
          the information being modeled is smaller than or
          equal to its minimum value.  If the information
          being modeled subsequently decreases below
          (increases above) the maximum (minimum) value, the
          Gauge32 also decreases (increases).";
      reference
         "RFC 2578, Sections 2. and 7.1.7.";
  };
  typedef Counter32 {
      type        Unsigned32;
      description
         "The Counter32 type represents a non-negative integer
          which monotonically increases until it reaches a
          maximum value of 2^32-1 (4294967295 decimal), when it
          wraps around and starts increasing again from zero.
          Counters have no defined `initial' value, and thus, a
          single value of a Counter has (in general) no information
          content.  Discontinuities in the monotonically increasing
          value normally occur at re-initialization of the
          management system, and at other times as specified in the
          description of an attribute using this type.  If such
          other times can occur, for example, the creation of a
          class instance that contains an attribute of type
          Counter32 at times other than re-initialization, then a
          corresponding attribute should be defined, with an
          appropriate type, to indicate the last discontinuity.
          Examples of appropriate types include: TimeStamp32,
          TimeStamp64, DateAndTime, TimeTicks32 or TimeTicks64
          (other types defined in this module).

Strauss & Schoenwaelder Experimental [Page 45] RFC 3780 SMIng May 2004

          The value of the access statement for attributes with
          a type value of Counter32 should be either `readonly'
          or `eventonly'.
          A default statement should not be used for attributes
          with a type value of Counter32.";
      reference
         "RFC 2578, Sections 2. and 7.1.6.";
  };
  typedef Gauge64 {
      type        Unsigned64;
      description
         "The Gauge64 type represents a non-negative integer,
          which may increase or decrease, but shall never
          exceed a maximum value, nor fall below a minimum
          value.  The maximum value can not be greater than
          2^64-1 (18446744073709551615), and the minimum value
          can not be smaller than 0.  The value of a Gauge64
          has its maximum value whenever the information
          being modeled is greater than or equal to its
          maximum value, and has its minimum value whenever
          the information being modeled is smaller than or
          equal to its minimum value.  If the information
          being modeled subsequently decreases below
          (increases above) the maximum (minimum) value, the
          Gauge64 also decreases (increases).";
  };
  typedef Counter64 {
      type        Unsigned64;
      description
         "The Counter64 type represents a non-negative integer
          which monotonically increases until it reaches a
          maximum value of 2^64-1 (18446744073709551615), when
          it wraps around and starts increasing again from zero.
          Counters have no defined `initial' value, and thus, a
          single value of a Counter has (in general) no
          information content.  Discontinuities in the
          monotonically increasing value normally occur at
          re-initialization of the management system, and at
          other times as specified in the description of an
          attribute using this type.  If such other times can
          occur, for example, the creation of a class
          instance that contains an attribute of type Counter32
          at times other than re-initialization, then
          a corresponding attribute should be defined, with an

Strauss & Schoenwaelder Experimental [Page 46] RFC 3780 SMIng May 2004

          appropriate type, to indicate the last discontinuity.
          Examples of appropriate types include: TimeStamp32,
          TimeStamp64, DateAndTime, TimeTicks32 or TimeTicks64
          (other types defined in this module).
          The value of the access statement for attributes with
          a type value of Counter64 should be either `readonly'
          or `eventonly'.
          A default statement should not be used for attributes
          with a type value of Counter64.";
      reference
         "RFC 2578, Sections 2. and 7.1.10.";
  };
  typedef Opaque {
      type        OctetString;
      status      obsolete;
      description
         "******* THIS TYPE DEFINITION IS OBSOLETE *******
          The Opaque type is provided solely for
          backward-compatibility, and shall not be used for
          newly-defined attributes and derived types.
          The Opaque type supports the capability to pass
          arbitrary ASN.1 syntax.  A value is encoded using
          the ASN.1 Basic Encoding Rules into a string of
          octets.  This, in turn, is encoded as an
          OctetString, in effect `double-wrapping' the
          original ASN.1 value.
          Note that a conforming implementation need only be
          able to accept and recognize opaquely-encoded data.
          It need not be able to unwrap the data and then
          interpret its contents.
          A requirement on `standard' modules is that no
          attribute may have a type value of Opaque and no
          type may be derived from the Opaque type.";
      reference
         "RFC 2578, Sections 2. and 7.1.9.";
  };
  typedef IpAddress {
      type        OctetString (4);
      status      deprecated;
      description

Strauss & Schoenwaelder Experimental [Page 47] RFC 3780 SMIng May 2004

         "******* THIS TYPE DEFINITION IS DEPRECATED *******
          The IpAddress type represents a 32-bit Internet
          IPv4 address.  It is represented as an OctetString
          of length 4, in network byte-order.
          Note that the IpAddress type is present for
          historical reasons.";
      reference
         "RFC 2578, Sections 2. and 7.1.5.";
  };
  typedef TimeTicks32 {
      type        Unsigned32;
      description
         "The TimeTicks32 type represents a non-negative integer
          which represents the time, modulo 2^32 (4294967296
          decimal), in hundredths of a second between two epochs.
          When attributes are defined which use this type, the
          description of the attribute identifies both of the
          reference epochs.
          For example, the TimeStamp32 type (defined in this
          module) is based on the TimeTicks32 type.";
      reference
         "RFC 2578, Sections 2. and 7.1.8.";
  };
  typedef TimeTicks64 {
      type        Unsigned64;
      description
         "The TimeTicks64 type represents a non-negative integer
          which represents the time, modulo 2^64
          (18446744073709551616 decimal), in hundredths of a second
          between two epochs.  When attributes are defined which use
          this type, the description of the attribute identifies
          both of the reference epochs.
          For example, the TimeStamp64 type (defined in this
          module) is based on the TimeTicks64 type.";
  };
  typedef TimeStamp32 {
      type        TimeTicks32;
      description
         "The value of an associated TimeTicks32 attribute at
          which a specific occurrence happened.  The specific
          occurrence must be defined in the description of any

Strauss & Schoenwaelder Experimental [Page 48] RFC 3780 SMIng May 2004

          attribute defined using this type.  When the specific
          occurrence occurred prior to the last time the
          associated TimeTicks32 attribute was zero, then the
          TimeStamp32 value is zero.  Note that this requires all
          TimeStamp32 values to be reset to zero when the value of
          the associated TimeTicks32 attribute reaches 497+ days
          and wraps around to zero.
          The associated TimeTicks32 attribute should be specified
          in the description of any attribute using this type.
          If no TimeTicks32 attribute has been specified, the
          default scalar attribute sysUpTime is used.";
      reference
         "RFC 2579, Section 2.";
  };
  typedef TimeStamp64 {
      type        TimeTicks64;
      description
         "The value of an associated TimeTicks64 attribute at which
          a specific occurrence happened.  The specific occurrence
          must be defined in the description of any attribute
          defined using this type.  When the specific occurrence
          occurred prior to the last time the associated TimeTicks64
          attribute was zero, then the TimeStamp64 value is zero.
          The associated TimeTicks64 attribute must be specified in
          the description of any attribute using this
          type. TimeTicks32 attributes must not be used as
          associated attributes.";
  };
  typedef TimeInterval32 {
      type        Integer32 (0..2147483647);
      description
         "A period of time, measured in units of 0.01 seconds.
          The TimeInterval32 type uses Integer32 rather than
          Unsigned32 for compatibility with RFC 2579.";
      reference
         "RFC 2579, Section 2.";
  };
  typedef TimeInterval64 {
      type        Integer64;
      description
         "A period of time, measured in units of 0.01 seconds.
          Note that negative values are allowed.";
  };

Strauss & Schoenwaelder Experimental [Page 49] RFC 3780 SMIng May 2004

  typedef DateAndTime {
      type        OctetString (8 | 11);
      default     0x0000000000000000000000;
      format      "2d-1d-1d,1d:1d:1d.1d,1a1d:1d";
      description
         "A date-time specification.
          field  octets  contents                  range
          -----  ------  --------                  -----
           1      1-2   year*                     0..65535
           2       3    month                     1..12 | 0
           3       4    day                       1..31 | 0
           4       5    hour                      0..23
           5       6    minutes                   0..59
           6       7    seconds                   0..60
                        (use 60 for leap-second)
           7       8    deci-seconds              0..9
           8       9    direction from UTC        '+' / '-'
           9      10    hours from UTC*           0..13
          10      11    minutes from UTC          0..59
  • Notes:
  1. the value of year is in big-endian encoding
  2. daylight saving time in New Zealand is +13
          For example, Tuesday May 26, 1992 at 1:30:15 PM EDT would
          be displayed as:
                       1992-5-26,13:30:15.0,-4:0
          Note that if only local time is known, then timezone
          information (fields 8-10) is not present.
          The two special values of 8 or 11 zero bytes denote an
          unknown date-time specification.";
      reference
         "RFC 2579, Section 2.";
  };
  typedef TruthValue {
      type        Enumeration (true(1), false(2));
      description
         "Represents a boolean value.";
      reference
         "RFC 2579, Section 2.";
  };
  typedef PhysAddress {

Strauss & Schoenwaelder Experimental [Page 50] RFC 3780 SMIng May 2004

      type        OctetString;
      format      "1x:";
      description
         "Represents media- or physical-level addresses.";
      reference
         "RFC 2579, Section 2.";
  };
  typedef MacAddress {
      type        OctetString (6);
      format      "1x:";
      description
         "Represents an IEEE 802 MAC address represented in the
          `canonical' order defined by IEEE 802.1a, i.e., as if it
          were transmitted least significant bit first, even though
          802.5 (in contrast to other 802.x protocols) requires MAC
          addresses to be transmitted most significant bit first.";
      reference
         "RFC 2579, Section 2.";
  };
  // The DisplayString definition below does not impose a size
  // restriction and is thus not the same as the DisplayString
  // definition in RFC 2579. The DisplayString255 definition is
  // provided for mapping purposes.
  typedef DisplayString {
      type        OctetString;
      format      "1a";
      description
         "Represents textual information taken from the NVT ASCII
          character set, as defined in pages 4, 10-11 of RFC 854.
          To summarize RFC 854, the NVT ASCII repertoire specifies:
  1. the use of character codes 0-127 (decimal)
  1. the graphics characters (32-126) are interpreted as

US ASCII

  1. NUL, LF, CR, BEL, BS, HT, VT and FF have the special

meanings specified in RFC 854

  1. the other 25 codes have no standard interpretation
  1. the sequence 'CR LF' means newline
  1. the sequence 'CR NUL' means carriage-return

Strauss & Schoenwaelder Experimental [Page 51] RFC 3780 SMIng May 2004

  1. an 'LF' not preceded by a 'CR' means moving to the

same column on the next line.

  1. the sequence 'CR x' for any x other than LF or NUL is

illegal. (Note that this also means that a string may

             end with either 'CR LF' or 'CR NUL', but not with CR.)
      ";
  };
  typedef DisplayString255 {
      type        DisplayString (0..255);
      description
         "A DisplayString with a maximum length of 255 characters.
          Any attribute defined using this syntax may not exceed 255
          characters in length.
          The DisplayString255 type has the same semantics as the
          DisplayString textual convention defined in RFC 2579.";
      reference
         "RFC 2579, Section 2.";
  };
  // The Utf8String and Utf8String255 definitions below facilitate
  // internationalization. The definition is consistent with the
  // definition of SnmpAdminString in RFC 2571.
  typedef Utf8String {
      type        OctetString;
      format      "65535t";      // is there a better way ?
      description
         "A human readable string represented using the ISO/IEC IS
          10646-1 character set, encoded as an octet string using
          the UTF-8 transformation format described in RFC 3629.
          Since additional code points are added by amendments to
          the 10646 standard from time to time, implementations must
          be prepared to encounter any code point from 0x00000000 to
          0x7fffffff.  Byte sequences that do not correspond to the
          valid UTF-8 encoding of a code point or are outside this
          range are prohibited.
          The use of control codes should be avoided. When it is
          necessary to represent a newline, the control code
          sequence CR LF should be used.
          The use of leading or trailing white space should be
          avoided.

Strauss & Schoenwaelder Experimental [Page 52] RFC 3780 SMIng May 2004

          For code points not directly supported by user interface
          hardware or software, an alternative means of entry and
          display, such as hexadecimal, may be provided.
          For information encoded in 7-bit US-ASCII, the UTF-8
          encoding is identical to the US-ASCII encoding.
          UTF-8 may require multiple bytes to represent a single
          character / code point; thus the length of a Utf8String in
          octets may be different from the number of characters
          encoded.  Similarly, size constraints refer to the number
          of encoded octets, not the number of characters
          represented by an encoding.";
  };
  typedef Utf8String255 {
      type        Utf8String (0..255);
      format      "255t";
      description
         "A Utf8String with a maximum length of 255 octets.  Note
          that the size of an Utf8String is measured in octets, not
          characters.";
  };
  identity null {
      description
         "An identity used to represent null pointer values.";
  };

};

Appendix B. SMIng ABNF Grammar

 The SMIng grammar conforms to the Augmented Backus-Naur Form (ABNF)
 [RFC2234].

;; ;; sming.abnf – SMIng grammar in ABNF notation (RFC 2234). ;; ;; @(#) $Id: sming.abnf,v 1.33 2003/10/23 19:31:55 strauss Exp $ ;; ;; Copyright (C) The Internet Society (2004). All Rights Reserved. ;;

smingFile = optsep *(moduleStatement optsep)

;; ;; Statement rules.

Strauss & Schoenwaelder Experimental [Page 53] RFC 3780 SMIng May 2004

;;

moduleStatement = moduleKeyword sep ucIdentifier optsep

                            "{" stmtsep
                            *(importStatement stmtsep)
                            organizationStatement stmtsep
                            contactStatement stmtsep
                            descriptionStatement stmtsep
                            *1(referenceStatement stmtsep)
                            1*(revisionStatement stmtsep)
                            *(extensionStatement stmtsep)
                            *(typedefStatement stmtsep)
                            *(identityStatement stmtsep)
                            *(classStatement stmtsep)
                        "}" optsep ";"

extensionStatement = extensionKeyword sep lcIdentifier optsep

                            "{" stmtsep
                            statusStatement stmtsep
                            descriptionStatement stmtsep
                            *1(referenceStatement stmtsep)
                            *1(abnfStatement stmtsep)
                        "}" optsep ";"

typedefStatement = typedefKeyword sep ucIdentifier optsep

                            "{" stmtsep
                            typedefTypeStatement stmtsep
                            *1(defaultStatement stmtsep)
                            *1(formatStatement stmtsep)
                            *1(unitsStatement stmtsep)
                            statusStatement stmtsep
                            descriptionStatement stmtsep
                            *1(referenceStatement stmtsep)
                        "}" optsep ";"

identityStatement = identityStmtKeyword sep lcIdentifier optsep

                            "{" stmtsep
                            *1(parentStatement stmtsep)
                            statusStatement stmtsep
                            descriptionStatement stmtsep
                            *1(referenceStatement stmtsep)
                        "}" optsep ";"

classStatement = classKeyword sep ucIdentifier optsep

                            "{" stmtsep
                            *1(extendsStatement stmtsep)
                            *(attributeStatement stmtsep)
                            *1(uniqueStatement stmtsep)

Strauss & Schoenwaelder Experimental [Page 54] RFC 3780 SMIng May 2004

  • (eventStatement stmtsep)

statusStatement stmtsep

                            descriptionStatement stmtsep
                            *1(referenceStatement stmtsep)
                        "}" optsep ";"

attributeStatement = attributeKeyword sep

                            lcIdentifier optsep
                            "{" stmtsep
                            typeStatement stmtsep
                            *1(accessStatement stmtsep)
                            *1(defaultStatement stmtsep)
                            *1(formatStatement stmtsep)
                            *1(unitsStatement stmtsep)
                            statusStatement stmtsep
                            descriptionStatement stmtsep
                            *1(referenceStatement stmtsep)
                        "}" optsep ";"

uniqueStatement = uniqueKeyword optsep

                            "(" optsep qlcIdentifierList
                            optsep ")" optsep ";"

eventStatement = eventKeyword sep lcIdentifier

                            optsep "{" stmtsep
                            statusStatement stmtsep
                            descriptionStatement stmtsep
                            *1(referenceStatement stmtsep)
                        "}" optsep ";"

importStatement = importKeyword sep ucIdentifier optsep

                            "(" optsep
                            identifierList optsep
                        ")" optsep ";"

revisionStatement = revisionKeyword optsep "{" stmtsep

                            dateStatement stmtsep
                            descriptionStatement stmtsep
                        "}" optsep ";"

typedefTypeStatement = typeKeyword sep refinedBaseType optsep ";"

typeStatement = typeKeyword sep

                        (refinedBaseType / refinedType) optsep ";"

parentStatement = parentKeyword sep qlcIdentifier optsep ";"

extendsStatement = extendsKeyword sep qucIdentifier optsep ";"

Strauss & Schoenwaelder Experimental [Page 55] RFC 3780 SMIng May 2004

dateStatement = dateKeyword sep date optsep ";"

organizationStatement = organizationKeyword sep text optsep ";"

contactStatement = contactKeyword sep text optsep ";"

formatStatement = formatKeyword sep format optsep ";"

unitsStatement = unitsKeyword sep units optsep ";"

statusStatement = statusKeyword sep status optsep ";"

accessStatement = accessKeyword sep access optsep ";"

defaultStatement = defaultKeyword sep anyValue optsep ";"

descriptionStatement = descriptionKeyword sep text optsep ";"

referenceStatement = referenceKeyword sep text optsep ";"

abnfStatement = abnfKeyword sep text optsep ";"

;; ;; ;;

refinedBaseType = ObjectIdentifierKeyword /

                        OctetStringKeyword *1(optsep numberSpec) /
                        PointerKeyword *1(optsep pointerSpec) /
                        Integer32Keyword *1(optsep numberSpec) /
                        Unsigned32Keyword *1(optsep numberSpec) /
                        Integer64Keyword *1(optsep numberSpec) /
                        Unsigned64Keyword *1(optsep numberSpec) /
                        Float32Keyword *1(optsep floatSpec) /
                        Float64Keyword *1(optsep floatSpec) /
                        Float128Keyword *1(optsep floatSpec) /
                        EnumerationKeyword
                                    optsep namedSignedNumberSpec /
                        BitsKeyword optsep namedNumberSpec

refinedType = qucIdentifier *1(optsep anySpec)

anySpec = pointerSpec / numberSpec / floatSpec

pointerSpec = "(" optsep qlcIdentifier optsep ")"

Strauss & Schoenwaelder Experimental [Page 56] RFC 3780 SMIng May 2004

numberSpec = "(" optsep numberElement

  • furtherNumberElement

optsep ")"

furtherNumberElement = optsep "|" optsep numberElement

numberElement = signedNumber *1numberUpperLimit

numberUpperLimit = optsep ".." optsep signedNumber

floatSpec = "(" optsep floatElement

  • furtherFloatElement

optsep ")"

furtherFloatElement = optsep "|" optsep floatElement

floatElement = floatValue *1floatUpperLimit

floatUpperLimit = optsep ".." optsep floatValue

namedNumberSpec = "(" optsep namedNumberList optsep ")"

namedNumberList = namedNumberItem

  • (optsep "," optsep namedNumberItem)

namedNumberItem = lcIdentifier optsep "(" optsep number

                            optsep ")"

namedSignedNumberSpec = "(" optsep namedSignedNumberList optsep ")"

namedSignedNumberList = namedSignedNumberItem

  • (optsep "," optsep

namedSignedNumberItem)

namedSignedNumberItem = lcIdentifier optsep "(" optsep signedNumber

                            optsep ")"

identifierList = identifier

  • (optsep "," optsep identifier)

qIdentifierList = qIdentifier

  • (optsep "," optsep qIdentifier)

qlcIdentifierList = qlcIdentifier

  • (optsep "," optsep qlcIdentifier)

bitsValue = "(" optsep bitsList optsep ")"

Strauss & Schoenwaelder Experimental [Page 57] RFC 3780 SMIng May 2004

bitsList = *1(lcIdentifier

  • (optsep "," optsep lcIdentifier))

;; ;; Other basic rules. ;;

identifier = ucIdentifier / lcIdentifier

qIdentifier = qucIdentifier / qlcIdentifier

ucIdentifier = ucAlpha *63(ALPHA / DIGIT / "-")

qucIdentifier = *1(ucIdentifier "::") ucIdentifier

lcIdentifier = lcAlpha *63(ALPHA / DIGIT / "-")

qlcIdentifier = *1(ucIdentifier "::") lcIdentifier

attrIdentifier = lcIdentifier *("." lcIdentifier)

qattrIdentifier = *1(ucIdentifier ".") attrIdentifier

cattrIdentifier = ucIdentifier "."

                            lcIdentifier *("." lcIdentifier)

qcattrIdentifier = qucIdentifier "."

                            lcIdentifier *("." lcIdentifier)

text = textSegment *(optsep textSegment)

textSegment = DQUOTE *textAtom DQUOTE

                        ; See Section 4.2.

textAtom = textVChar / HTAB / SP / lineBreak

date = DQUOTE 4DIGIT "-" 2DIGIT "-" 2DIGIT

  • 1(" " 2DIGIT ":" 2DIGIT)

DQUOTE

                        ; always in UTC

format = textSegment

units = textSegment

anyValue = bitsValue /

                        signedNumber /
                        hexadecimalNumber /

Strauss & Schoenwaelder Experimental [Page 58] RFC 3780 SMIng May 2004

                        floatValue /
                        text /
                        objectIdentifier
                        ; Note: `objectIdentifier' includes the
                        ; syntax of enumeration labels and
                        ; identities.
                        ; They are not named literally to
                        ; avoid reduce/reduce conflicts when
                        ; building LR parsers based on this
                        ; grammar.

status = currentKeyword /

                        deprecatedKeyword /
                        obsoleteKeyword

access = eventonlyKeyword /

                        readonlyKeyword /
                        readwriteKeyword

objectIdentifier = (qlcIdentifier / subid "." subid)

  • 127("." subid)

subid = decimalNumber

number = hexadecimalNumber / decimalNumber

negativeNumber = "-" decimalNumber

signedNumber = number / negativeNumber

decimalNumber = "0" / (nonZeroDigit *DIGIT)

zeroDecimalNumber = 1*DIGIT

hexadecimalNumber = %x30 %x78 ; "0x" with x only lower-case

                        1*(HEXDIG HEXDIG)

floatValue = neginfKeyword /

                        posinfKeyword /
                        snanKeyword /
                        qnanKeyword /
                        signedNumber "." zeroDecimalNumber
                            *1("E" ("+"/"-") zeroDecimalNumber)

;; ;; Rules to skip unknown statements ;; with arbitrary arguments and blocks. ;;

Strauss & Schoenwaelder Experimental [Page 59] RFC 3780 SMIng May 2004

unknownStatement = unknownKeyword optsep *unknownArgument

                            optsep ";"

unknownArgument = ("(" optsep unknownList optsep ")") /

                        ("{" optsep *unknownStatement optsep "}") /
                        qucIdentifier /
                        anyValue /
                        anySpec

unknownList = namedNumberList /

                        qIdentifierList

unknownKeyword = lcIdentifier

;; ;; Keyword rules. ;; ;; Typically, keywords are represented by tokens returned from the ;; lexical analyzer. Note, that the lexer has to be stateful to ;; distinguish keywords from identifiers depending on the context ;; position in the input stream. ;;

moduleKeyword = %x6D %x6F %x64 %x75 %x6C %x65 importKeyword = %x69 %x6D %x70 %x6F %x72 %x74 revisionKeyword = %x72 %x65 %x76 %x69 %x73 %x69 %x6F %x6E dateKeyword = %x64 %x61 %x74 %x65 organizationKeyword = %x6F %x72 %x67 %x61 %x6E %x69 %x7A %x61 %x74

                     %x69 %x6F %x6E

contactKeyword = %x63 %x6F %x6E %x74 %x61 %x63 %x74 descriptionKeyword = %x64 %x65 %x73 %x63 %x72 %x69 %x70 %x74 %x69

                     %x6F %x6E

referenceKeyword = %x72 %x65 %x66 %x65 %x72 %x65 %x6E %x63 %x65 extensionKeyword = %x65 %x78 %x74 %x65 %x6E %x73 %x69 %x6F %x6E typedefKeyword = %x74 %x79 %x70 %x65 %x64 %x65 %x66 typeKeyword = %x74 %x79 %x70 %x65 parentKeyword = %x70 %x61 %x72 %x65 %x6E %x74 identityStmtKeyword = %x69 %x64 %x65 %x6E %x74 %x69 %x74 %x79 classKeyword = %x63 %x6C %x61 %x73 %x73 extendsKeyword = %x65 %x78 %x74 %x65 %x6E %x64 %x73 attributeKeyword = %x61 %x74 %x74 %x72 %x69 %x62 %x75 %x74 %x65 uniqueKeyword = %x75 %x6E %x69 %x71 %x75 %x65 eventKeyword = %x65 %x76 %x65 %x6E %x74 formatKeyword = %x66 %x6F %x72 %x6D %x61 %x74 unitsKeyword = %x75 %x6E %x69 %x74 %x73 statusKeyword = %x73 %x74 %x61 %x74 %x75 %x73 accessKeyword = %x61 %x63 %x63 %x65 %x73 %x73 defaultKeyword = %x64 %x65 %x66 %x61 %x75 %x6C %x74

Strauss & Schoenwaelder Experimental [Page 60] RFC 3780 SMIng May 2004

abnfKeyword = %x61 %x62 %x6E %x66

;; Base type keywords.

OctetStringKeyword = %x4F %x63 %x74 %x65 %x74 %x53 %x74 %x72 %x69

                     %x6E %x67

PointerKeyword = %x50 %x6F %x69 %x6E %x74 %x65 %x72 ObjectIdentifierKeyword = %x4F %x62 %x6A %x65 %x63 %x74 %x49 %x64

                     %x65 %x6E %x74 %x69 %x66 %x69 %x65 %x72

Integer32Keyword = %x49 %x6E %x74 %x65 %x67 %x65 %x72 %x33 %x32 Unsigned32Keyword = %x55 %x6E %x73 %x69 %x67 %x6E %x65 %x64 %x33

                     %x32

Integer64Keyword = %x49 %x6E %x74 %x65 %x67 %x65 %x72 %x36 %x34 Unsigned64Keyword = %x55 %x6E %x73 %x69 %x67 %x6E %x65 %x64 %x36

                     %x34

Float32Keyword = %x46 %x6C %x6F %x61 %x74 %x33 %x32 Float64Keyword = %x46 %x6C %x6F %x61 %x74 %x36 %x34 Float128Keyword = %x46 %x6C %x6F %x61 %x74 %x31 %x32 %x38 BitsKeyword = %x42 %x69 %x74 %x73 EnumerationKeyword = %x45 %x6E %x75 %x6D %x65 %x72 %x61 %x74 %x69

                     %x6F %x6E

;; Status keywords.

currentKeyword = %x63 %x75 %x72 %x72 %x65 %x6E %x74 deprecatedKeyword = %x64 %x65 %x70 %x72 %x65 %x63 %x61 %x74 %x65

                     %x64

obsoleteKeyword = %x6F %x62 %x73 %x6F %x6C %x65 %x74 %x65

;; Access keywords.

eventonlyKeyword = %x65 %x76 %x65 %x6E %x74 %x6F %x6E %x6C %x79 readonlyKeyword = %x72 %x65 %x61 %x64 %x6F %x6E %x6C %x79 readwriteKeyword = %x72 %x65 %x61 %x64 %x77 %x72 %x69 %x74 %x65

;; Special floating point values' keywords.

neginfKeyword = %x6E %x65 %x67 %x69 %x6E %x66 posinfKeyword = %x70 %x6F %x73 %x69 %x6E %x66 snanKeyword = %x73 %x6E %x61 %x6E qnanKeyword = %x71 %x6E %x61 %x6E

;; ;; Some low level rules. ;; These tokens are typically skipped by the lexical analyzer. ;;

Strauss & Schoenwaelder Experimental [Page 61] RFC 3780 SMIng May 2004

sep = 1*(comment / lineBreak / WSP)

                        ; unconditional separator

optsep = *(comment / lineBreak / WSP)

stmtsep = *(comment /

                          lineBreak /
                          WSP /
                          unknownStatement)

comment = "" *(WSP / VCHAR) lineBreak lineBreak = CRLF / LF ;; ;; Encoding specific rules. ;; textVChar = %x21 / %x23-7E ; any VCHAR except DQUOTE ucAlpha = %x41-5A lcAlpha = %x61-7A nonZeroDigit = %x31-39 ;; ;; RFC 2234 core rules. ;; ALPHA = %x41-5A / %x61-7A ; A-Z / a-z CR = %x0D ; carriage return CRLF = CR LF ; Internet standard newline DIGIT = %x30-39 ; 0-9 DQUOTE = %x22 ; " (Double Quote) HEXDIG = DIGIT / %x61 / %x62 / %x63 / %x64 / %x65 / %x66 Strauss & Schoenwaelder Experimental [Page 62] RFC 3780 SMIng May 2004 ; only lower-case a..f HTAB = %x09 ; horizontal tab LF = %x0A ; linefeed SP = %x20 ; space VCHAR = %x21-7E ; visible (printing) characters WSP = SP / HTAB ; white space ;; End of ABNF Authors' Addresses Frank Strauss TU Braunschweig Muehlenpfordtstrasse 23 38106 Braunschweig Germany Phone: +49 531 391 3266 EMail: strauss@ibr.cs.tu-bs.de URI: http://www.ibr.cs.tu-bs.de/ Juergen Schoenwaelder International University Bremen P.O. Box 750 561 28725 Bremen Germany Phone: +49 421 200 3587 EMail: j.schoenwaelder@iu-bremen.de URI: http://www.eecs.iu-bremen.de/ Strauss & Schoenwaelder Experimental [Page 63] RFC 3780 SMIng May 2004 Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf- ipr@ietf.org. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Strauss & Schoenwaelder Experimental [Page 64]

/data/webs/external/dokuwiki/data/pages/rfc/rfc3780.txt · Last modified: 2004/05/13 16:33 by 127.0.0.1

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